text
stringlengths 4
179k
| predicted_class
stringclasses 5
values | confidence
float64 0
100
|
|---|---|---|
Because of the difference in the oxidation state, antimony halide perovskites have the basic formula A3Sb2X9 (X = Cl, Br, I), where A are organic (e.g. NH4 + , CH3NH3 + [55, 158], dimethylammonium , trimethylammonium , tetramethylammonium , guanidinium ) or inorganic (e.g. Rb+ [35, 162], Cs+ [65, 162–164]) cations. The structural chemistry and dimensionality of antimony halide perovskites are significantly influenced by the choice of cationic and anionic species. Depending on the dimensionality, the crystal structures of antimony-based perovskites featuring Sb2X9 3− enneahalide ions within the anionic sublattice can be divided into three categories (Fig. 9) [159, 163]:Fig. 9Anionic sublattices present in antimony halide perovskites in polyhedral representation: a zero-dimensional dimers of face-sharing octahedra, b one-dimensional double chains of corner-connected octahedra, and c two-dimensional double-layered structures of corner-sharing octahedra. Reproduced with permission of the International Union of Crystallography . Copyright (1996) International Union of Crystallography zero-dimensional, isolated double octahedral structures comprising pairs of face-sharing SbX6 octahedra, which form discrete complex anionic metal halide Sb2X9 3− clusters arranged in dimer units (e.g. (CH3NH3)3Sb2I9 , [N(CH3)4]3Sb2Cl9 , Cs3Sb2I9 [163–165]);infinite one-dimensional double chains of corner-sharing SbX6 octahedra forming zigzag-type polyanionic Sb2X9 3− sublattices (e.g. (CH3NH3)3Sb2Cl9 );two-dimensional corrugated double-layered polyanionic structures based on corner-connected SbX6 octahedra to give Sb2X9 3− sub-units (e.g. (NH4)3Sb2I9 , [NH(CH3)3]3Sb2Cl9 , Rb3Sb2I9 , Cs3Sb2I9 [163–165]).
|
other
| 28.52 |
Anionic sublattices present in antimony halide perovskites in polyhedral representation: a zero-dimensional dimers of face-sharing octahedra, b one-dimensional double chains of corner-connected octahedra, and c two-dimensional double-layered structures of corner-sharing octahedra. Reproduced with permission of the International Union of Crystallography . Copyright (1996) International Union of Crystallography
|
study
| 34.44 |
zero-dimensional, isolated double octahedral structures comprising pairs of face-sharing SbX6 octahedra, which form discrete complex anionic metal halide Sb2X9 3− clusters arranged in dimer units (e.g. (CH3NH3)3Sb2I9 , [N(CH3)4]3Sb2Cl9 , Cs3Sb2I9 [163–165]);
|
other
| 28.03 |
The optoelectronic properties of (CH3NH3)3Sb2I9 have been investigated by Hebig et al. recently . The compound has a zero-dimensional dimer structure comprising discrete bi-octahedral metal halide units Sb2I9 3− of face-sharing BI6 octahedra surrounded by CH3NH3 + cations to balance the charge neutrality. The complex anionic clusters are interconnected via hydrogen bonding interactions of the type N–H···I. (CH3NH3)3Sb2I9 was prepared via a solution-based deposition method from CH3NH3I and SbI3 at low temperatures (100–120 °C). The peak absorption coefficient is approximately 105 cm−1 and thereby in a similar range compared to the lead-based analogue . The optical band gap was determined to be 2.14 eV assuming a direct band transition. (CH3NH3)3Sb2I9 was implemented as absorber material in planar heterojunction solar cells (ITO/PEDOT:PSS/(CH3NH3)2Sb2I9 (300 nm)/PC61BM/ZnO-NP/Al) to yield a V OC of 890 mV, a J SC of 1.1 mA cm−2, a FF of 55%, and a PCE of ca. 0.5% (Fig. 10). In addition, a maximum external quantum efficiency (EQE) of about 12%, and only little hysteresis in planar perovskite solar cells are reported . The authors attributed this low photocurrent density to an inefficient charge extraction, which might be improved using mesoporous scaffolds.Fig. 10 a J–V curves of (CH3NH3)3Sb2I9-based perovskite solar cells scanned in forward and reverse direction, and b corresponding EQE spectra including a reference device without absorber material. Adapted with permission from . Copyright (2016) American Chemical Society
|
study
| 30.56 |
a J–V curves of (CH3NH3)3Sb2I9-based perovskite solar cells scanned in forward and reverse direction, and b corresponding EQE spectra including a reference device without absorber material. Adapted with permission from . Copyright (2016) American Chemical Society
|
study
| 34.28 |
In addition, the processing methodology has an influence on the obtained structure. For example, in the case of Cs3Sb2I9, zero-dimensional dimer species are obtained from solution-based methods, while two-dimensional layered perovskites can be prepared by co-evaporation or solid-state reactions . Due to the prevalence of polymorphism (e.g. [NH2(CH3)2]3Sb2Cl9 , Rb3Sb2I9 [35, 162], Cs3Sb2I9 ) in this class of perovskites, this dependence of the dimensionality on the processing parameters is an important issue to improve the materials properties (e.g. charge transport) for photovoltaic applications.
|
other
| 28.88 |
A variety of antimony halide perovskites has been investigated with regard to the crystal structure [157, 160, 164, 166], phase transitions of polymorphous compounds [158, 159, 163, 165, 166], as well as ferroelectric and optical properties [162, 167, 168]. Only a few studies aim at a photovoltaic application [35, 55, 65].
|
study
| 27.05 |
Harikesh et al. have recently reported the synthesis of Rb3Sb2I9 in a layered perovskite structure via a low-temperature solution-based route through the reaction of RbI and SbI3 . In comparison to the dimer modification of Cs3Sb2I9, the substitution of Cs+ (188 pm) with the smaller Rb+ (172 pm) cation was shown to effectively stabilize the structure in the layered modification. As a consequence, the respective Rb3Sb2I9 perovskite forms a two-dimensional layered structure consisting of corner-sharing BX6 octahedra, which is different to the zero-dimensional dimer modification of Cs3Sb2I9 comprising isolated bi-octahedral metal halide units B2X9 3− (Fig. 11) [35, 51].Fig. 11 a Schematic representation of the influence of the ionic radius of the A-site cation on the structure and dimensionality of A3Sb2I9-type perovskite compounds, and b J–V curves of Rb3Sb2I9-based solar cells under illuminated and dark conditions in forward and reverse scan direction (inset energy level diagram). Reprinted with permission from . Copyright (2016) American Chemical Society
|
study
| 29 |
a Schematic representation of the influence of the ionic radius of the A-site cation on the structure and dimensionality of A3Sb2I9-type perovskite compounds, and b J–V curves of Rb3Sb2I9-based solar cells under illuminated and dark conditions in forward and reverse scan direction (inset energy level diagram). Reprinted with permission from . Copyright (2016) American Chemical Society
|
study
| 34.22 |
Peresh et al. investigated the optical properties of inorganic A3Sb2Br9-type antimony halide perovskites and determined band gaps of 2.48 eV (A = Rb+) and 2.30 eV (A = Cs+) . By substitution of Br− with the heavier I–, the band gap can be shifted down to 1.89 eV for Cs3Sb2I9, which is a promising value for photovoltaic applications.
|
other
| 31.72 |
Saparov et al. examined Cs3Sb2I9 as prospective absorber material in solar cells and found improved stability properties under ambient conditions compared to lead and tin halide perovskite films . Cs3Sb2I9 exists in two polymorphs: (1) a zero-dimensional dimer modification (hexagonal) featuring Sb2I9 3− bi-octahedral units and (2) a two-dimensional layered modification (trigonal) . The dimer can be synthesized via solution-based methods using polar solvents, while the layered modification is obtained through solid-state reactions, gas phase reactions (e.g. co-evaporation or sequential deposition of CsI and SbI3, followed by annealing in SbI3 vapor) or solution-based methods (e.g. crystallization from methanol or non-polar solvents) [65, 163]. According to electronic band structure calculations, the dimer modification has an indirect band gap of 2.40 eV (HSE, Heyd–Scuseria–Ernzerhof), while the layered polymorph exhibits a nearly direct band gap of 2.06 eV (HSE). This latter value is in good agreement with the experimental value of 2.05 eV found for the layered polymorph . Saparov et al. investigated the layered modification of Cs3Sb2I9 as light absorber in perovskite solar cells with the general device architecture of FTO/c-TiO2/Cs3Sb2I9/PTAA/Au (PTAA: poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine]). The material exhibited a rather poor photovoltaic performance with a V OC up to 300 mV, a J SC below 0.1 mA cm−2 and a low overall performance (<1%) .
|
study
| 30.39 |
The substitution of Cs+ with Rb+ in A3Sb2X9-type perovskites is accompanied by only a small blueshift of the band gap. Experimentally, an indirect band gap of 2.1 eV and a direct transition at 2.24 eV was determined for Rb3Sb2I9 compared to a value of 2.05 eV for the band gap of the cesium analogue . In addition, Rb3Sb2I9 exhibits an absorption coefficient over 1 × 105 cm−1, which is in a similar range compared to lead-based systems . Harikesh et al. examined solution-processed Rb3Sb2I9 perovskite absorbers in solar cells with an FTO/c-TiO2/mp-TiO2/Rb3Sb2I9/poly-TPD/Au device architecture (poly-TPD: poly[N,N′-bis(4-butylphenyl)-N,N′-bisphenylbenzidine]). The solar cells exhibited a V OC of 0.55 V, a J SC of 2.12 mA cm−2, and a FF of 57% resulting in a PCE of 0.66% (Fig. 11) . These are quite promising results for alternative lead-free perovskite semiconductors.
|
study
| 29.95 |
Mitzi et al. investigated metal-deficient antimony and bismuth-based hybrid perovskites with the chemical formula (H2AEQT)B2/3I4 (B = Sb, Bi; AEQT = 5,5′′′-bis-(aminoethyl)-2,2′:5′,2′′:5′′,2′′′-quaterthiophene) . This class of layered perovskites consists of inorganic metal-deficient metal halide layers (B2/3X4 2−) alternating with layers of the organic H2AEQT2+ cation to form a two-dimensional structure . In addition, vacancies on the metal site within the inorganic sheets together with the rigid organic AEQT-based layers were found to play an essential role in stabilizing the two-dimensional metal-deficient perovskite structure .
|
other
| 32.75 |
Antimony halide double perovskite semiconductors with a basic formula A2BIBIIX6 have been investigated in a theoretical study by Volonakis et al. . These materials are based on a heterovalent substitution of Pb2+ with an equal number of mono- and trivalent cations to maintain the charge neutrality and form double perovskite structures (elpasolite structure). Volonakis et al. examined halide double perovskites based on monovalent noble metals (BI = Cu+, Ag+, Au+) and trivalent pnictogen cations (BII = Sb3+, Bi3+) with Cs+ as A-site cation and halide (X = Cl, Br, I) as counterions . The noble-metal and pnictogen cations occupy the BI and BII sites, which alternate along the three crystallographic axes giving rock-salt ordering . The calculated electronic band gaps of the examined antimony halide double perovskites are indirect band gaps and tunable in the visible range, i.e. 0.9–2.1 eV (Cs2CuSbX6), 1.1–2.6 eV (Cs2AgSbX6), and 0.0–1.3 eV (Cs2AuSbX6) .
|
study
| 30.17 |
A summary of structural and optical data of antimony halide perovskites and their performance as absorber material in solar cells is given in Table 8.Table 8Structural and optical data of antimony halide perovskites and the obtained PCEs (if applied in photovoltaic devices)PerovskiteSim./exp.Crystal system (space group)DimensionalityBand gap/eVPCE/%References(NH4)3Sb2I9 Exp.Monoclinic (P21/n)2D––(CH3NH3)3Sb2Cl9 Exp.Orthorhombic (Pmcn)1D––[158, 166](CH3NH3)3Sb2Br9 Exp.Trigonal (P \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\bar{3}$$\end{document}3¯ m1)2D––(CH3NH3)3Sb2I9 Exp.Hexagonal (P63/mmc)0D2.14ca. 0.5[55, 163][NH2(CH3)2]3Sb2Cl9 Exp.Monoclinic (Pc) at 200 K–––Monoclinic (P21/c) at 298 K2D––[159, 168][NH2(CH3)2]3Sb2Br9 Exp.Monoclinic (P21/c)–––[NH(CH3)3]3Sb2Cl9 Exp.Monoclinic (Pc)2D––[N(CH3)4]3Sb2Cl9 Exp.Hexagonal (P63/mmc)0D––[N(CH3)4]3Sb2Br9 Exp.Hexagonal (P63/mmc)0D––(C5H5NH)3Sb2Cl9 Exp.Monoclinic (C2/c)1D––Rb3Sb2Br9 Exp.Trigonal (P \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\bar{3}$$\end{document}3¯ m1)–2.48–Rb3Sb2I9 Sim./exp.Monoclinic (Pc)2D2.10.66Monoclinic (Pc)–1.94–α-Cs3Sb2Cl9 Exp.Trigonal (P321)2D––β-Cs3Sb2Cl9 Exp.Orthorhombic (Pmcn)1D––Cs3Sb2Br9 Exp.Trigonal (P \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\bar{3}$$\end{document}3¯ m1)–2.30–Cs3Sb2I9 Sim./exp.Hexagonal (P63/mmc)0D1.89–2.4<1[65, 162–164]Trigonal (P \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\bar{3}$$\end{document}3¯ m1)2D2.05Cs2CuSbX6 (X = Cl, Br, I)Sim.Cubic (Fm \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\bar{3}$$\end{document}3¯ m)3D2.1 (X = Cl)–1.6 (X = Br)0.9 (X = I)Cs2AgSbX6 (X = Cl, Br, I)Sim.Cubic (Fm \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\bar{3}$$\end{document}3¯ m)3D2.6 (X = Cl)–1.9 (X = Br)1.1 (X = I)Cs2AuSbX6 (X = Cl, Br, I)Sim.Cubic (Fm \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\bar{3}$$\end{document}3¯ m)3D1.3 (X = Cl)–0.7 (X = Br)0 (X = I)(H2AEQT)Sb2/3I4 Exp.Monoclinic (C2/m)2 D––[C(NH2)3]3[Sb2I9]Exp.Orthorhombic (Cmcm) at 293 K–––Exp.Orthorhombic (Cmcm) at 348 KExp.Hexagonal (P63/mmc) at 364 K
|
clinical case
| 29.44 |
The group-15 metal bismuth is an interesting replacement candidate for lead and tin, which is supported by various aspects : The trivalent Bi3+ ion (1) is isoelectronic to Pb2+ (6s2 6p0 electronic configuration) featuring the same 6s2 lone pair, (2) shows a similar electronegativity (Bi: 2.02, Pb: 2.33, Sn: 1.96), and (3) has an ionic radius (103 pm) comparable to Pb2+ (119 pm) and Sn2+ (110 pm) metal cations [28, 51, 125].
|
other
| 28.03 |
However, the trivalent Bi3+ ion cannot directly replace the divalent Pb2+ ion in the perovskite structure due to the different valence state. Bismuth halide perovskites exhibit a huge structural diversity in terms of connectivity (face-, edge- or corner-sharing networks) and dimensionality ranging from zero-dimensional dimer units, to one-dimensional chain-like motifs or two-dimensional layered networks up to three-dimensional double perovskite frameworks (elpasolite structure) .
|
other
| 28.98 |
Zero-dimensional bismuth halide perovskites with a basic formula unit A3Bi2X9 crystallize in the Cs3Cr2Cl9 structure type. This crystal structure is based on the hexagonal closest packing of A and X atoms forming hexagonally stacked AX3 layers with trivalent metal cations occupying two-thirds of the emerging octahedral sites, while one-third of the remaining metal sites are vacant. In this way, double octahedral structures are obtained consisting of pairs of face-sharing BiX6 octahedra to give complex Bi2X9 3− anionic clusters, which are referred to as isolated metal halide dimer units. The resulting discrete anionic bi-octahedral moieties are surrounded by monovalent cations occupying the A-site of the perovskite structure [36, 66, 162, 164, 175–178]. Several zero-dimensional bismuth halide perovskites have been reported so far incorporating a range of different cations such as CH3NH3 + , guanidinium , cyclohexylammonium , K+ , Rb+ , or Cs+ [36, 66].
|
study
| 27.77 |
The most intensively studied bismuth halide perovskite in terms of optoelectronic applications is (CH3NH3)3Bi2I9. Single crystals can be synthesized via a layered-solution crystallization technique [176, 180], while thin films are obtained from solution-based processing (e.g. spin coating, doctor blading) followed by subsequent thermal annealing at low temperatures [36, 175, 181–184] or via vapor-assisted methods . The (CH3NH3)3Bi2I9 structure consists of pairs of face-sharing BiI6 octahedra forming isolated metal halide dimer units of Bi2I9 3− surrounded by randomly disordered CH3NH3 + cations [175, 177, 180, 182]. The bi-octahedral anionic clusters are interconnected via N–H···I hydrogen bonding interactions [179, 182]. Dipolar ordering of the organic cation and in-plane ordering of the lone pair of the metal upon cooling is accompanied by phase transitions from a hexagonal crystal structure (space group: P63/mmc) at 300 K to a monoclinic crystal structure (space group: C2/c) at 160 K with an additional first-order phase transition at 143 K (monoclinic, space group: P21) .
|
study
| 28.55 |
(CH3NH3)3Bi2I9 is an environmentally friendly semiconductor with promising stability in ambient atmosphere and under humid conditions [36, 175, 180, 181, 183, 184]. With regard to the electronic band structure, DFT calculations predict an indirect character of the band gap with values of ca. 2.25 eV [175, 181], which are in good agreement with the experimental values (1.94-2.11 eV) [175, 176, 181]. In addition, (CH3NH3)3Bi2I9 exhibits a strong absorption band around 500 nm, a pre-edge absorption peak at 2.51 eV indicating the existence of intrinsic excitons, and a high optical absorption coefficient in the order of 105 cm−1 comparable to that of lead-based analogues [36, 169, 176, 177, 184]. However, the exciton binding energy of more than 300 meV , which is in good agreement with time-dependent DFT calculations (400 meV) , is much larger than in lead-based analogues (ca. 40 meV ) and thus limits the photovoltaic performance up to now.
|
study
| 29.33 |
The potential of (CH3NH3)3Bi2I9 as lead-free absorber material for photovoltaic applications has been explored in planar [182, 184] and meso-structured [36, 175, 184] device configurations using diverse electron (e.g. TiO2 [36, 175, 183, 184], PCBM ) and hole (e.g. Spiro-OMeDAT [36, 183, 184], P3HT , PEDOT:PSS ) transport layers as well as the transparent conductive oxides FTO [36, 175, 183, 184] or ITO [182, 183].
|
review
| 27.34 |
Öz et al. investigated (CH3NH3)3Bi2I9 in planar heterojunction solar cells in inverted geometry (ITO/PEDOT:PSS/(CH3NH3)3Bi2I9/PCBM/Ca/Al) and obtained a V OC of 0.66 V, a FF of 49%, and a PCE of about 0.1% (Fig. 12) . The photovoltaic performance is currently limited by the relatively low J SC of 0.22 mA cm−2, which is due to the high exciton binding energy and ineffective charge separation in planar configurations .Fig. 12 a Energy level diagram and b J–V curves under illumination of a photovoltaic device with a (CH3NH3)3Bi2I9-based absorber material (blue) and a reference solar cell without absorber (black). Adapted with permission from . Copyright (2016) Elsevier
|
study
| 29.08 |
In case of planar heterojunction solar cells with a general device architecture of FTO/TiO2/(CH3NH3)3Bi2I9/P3HT/Au a V OC of 0.51 V, a J SC of 0.36 mA cm−2, a FF of 44.4%, and a PCE of 0.08% could be achieved . In perovskite solar cells (FTO/TiO2/mp-TiO2/perovskite/P3HT/Au) employing thick mesoporous TiO2 layers (1.8 µm), the photovoltaic performance can be improved yielding a V OC of 0.35 V, a J SC of 1.16 mA cm−2, a FF of 46.4%, and a PCE of ca. 0.19% .
|
review
| 26.69 |
a Cross-sectional SEM image of a (CH3NH3)3Bi2I9-based perovskite solar cell in meso-structured configuration (ITO/c-TiO2/mp-TiO2/(CH3NH3)3Bi2I9/Spiro-OMeTAD/MoO3/Ag, scale bar 1 µm), b J–V curve under illumination (100 mW/cm2). Adapted with permission from . Copyright (2016) Springer
|
clinical case
| 32.62 |
Park et al. expanded the research to mixed halide pervoskites such as (CH3NH3)3Bi2I9−xClx . Due to the partial substitution of iodide with chloride in (CH3NH3)3Bi2I9−xClx, the band gap was shifted from 2.1 eV (X = I) to 2.4 eV (X = Cl, I) assuming a direct character of the band gap in both cases . The photovoltaic performance in a meso-structured device architecture (FTO/c-TiO2/mp-TiO2/perovskite/Spiro-OMeDAT/Ag), however, was significantly lower (0.003%) compared to (CH3NH3)3Bi2I9 (0.12%), which can be attributed to the low V OC of only 40 mV (Fig. 14) .Fig. 14 a J–V curves and b IPCE spectra of perovskite solar cells in meso-structured configuration using (CH3NH3)3Bi2I9−xClx, (CH3NH3)3Bi2I9, and Cs3Bi2I9 absorber materials, respectively. Adapted with permission from . Copyright (2015) WILEY–VCH Verlag GmbH & Co. KGaA, Weinheim
|
other
| 28.83 |
Singh et al. evaluated the effect of various types of TiO2 (anatase, brookite) and architectures (planar, mesoporous) of ETLs on the film morphology and photovoltaic performance in solar cells (FTO/TiO2/(CH3NH3)3Bi2I9/Spiro-OMeDAT/Au) . The implementation of a mesoporous anatase TiO2 scaffold was reported to significantly improve the J SC (ca. 0.8 mA cm−2) and the efficiency (0.2%) compared to planar and mesoporous brookite perovskite solar cells. Almost no J–V hysteresis was determined irrespective of the type and architecture of the ETL. In addition, the solar cells were found to be moderately stable under ambient conditions without any sealing for more than 10 weeks .
|
other
| 29.3 |
Zhang et al. reported enhanced PCE values using ITO and a modified annealing procedure of the ETL instead of FTO as transparent contact . In addition, the processing conditions and the structure of the ETL (planar or meso-structured) play a key role for the morphology of the active layer and consequently for the photovoltaic performance. The PCE was improved from 0.14% in planar architecture (ITO/c-TiO2/(CH3NH3)3Bi2I9/Spiro-OMeTAD/MoO3/Ag) to 0.42% in the meso-structured configuration (ITO/c-TiO2/mp-TiO2/(CH3NH3)3Bi2I9/Spiro-OMeTAD/MoO3/Ag, Fig. 13) .Fig. 13 a Cross-sectional SEM image of a (CH3NH3)3Bi2I9-based perovskite solar cell in meso-structured configuration (ITO/c-TiO2/mp-TiO2/(CH3NH3)3Bi2I9/Spiro-OMeTAD/MoO3/Ag, scale bar 1 µm), b J–V curve under illumination (100 mW/cm2). Adapted with permission from . Copyright (2016) Springer
|
other
| 29.72 |
a J–V curves and b IPCE spectra of perovskite solar cells in meso-structured configuration using (CH3NH3)3Bi2I9−xClx, (CH3NH3)3Bi2I9, and Cs3Bi2I9 absorber materials, respectively. Adapted with permission from . Copyright (2015) WILEY–VCH Verlag GmbH & Co. KGaA, Weinheim
|
clinical case
| 29.22 |
Moreover, the zero-dimensional dimer species of Cs3Bi2I9 was investigated previously with regard to the crystal structure and phase transitions [165, 178]. Recently, Cs3Bi2I9 has attracted substantial attention as alternative lead-free absorber for photovoltaic applications. Park et al. implemented Cs3Bi2I9 in meso-structured perovskite solar cells (FTO/c-TiO2/mp-TiO2/perovskite/Spiro-OMeDAT/Ag) and obtained a record efficiency of 1.09% for a bismuth halide perovskite solar cell (Fig. 14) . Cs3Bi2I9 showed improved photovoltaic characteristics compared to the methylammonium analogue (Fig. 14a). In addition, while almost no J–V hysteresis was found directly after device fabrication, a pronounced hysteretic behavior was observed after a month. However, the PCE was shown to be highly stable with no decay even after storage under dry conditions during a month. Thus, Cs3Bi2I9 and other zero-dimensional analogues might be suitable candidates for solution-processed absorber materials to substitute lead-based perovskites.
|
study
| 29.2 |
One-dimensional bismuth halide perovskites exist in two different structures: (1) in form of BiX4 − anionic chains built of edge-sharing BiX6 octahedra alternating with cationic species to balance the charge neutrality (e.g. LiBiI4·5 H2O ) or (2) as bismuth halide chains of distorted BiX6 octahedra in zigzag conformation, which are interconnected by dicationic alkyldiammonium species occupying the A-site positions (e.g. HDABiI5 ).
|
other
| 27.2 |
The first motif can be found in LiBiI4·5 H2O, MgBi2I8·8 H2O, MnBi2I8·8 H2O, and KBiI4·H2O, which were studied by Yelovik et al. . The optical band gaps of the four compounds were determined to be between 1.70 and 1.76 eV, which is in good agreement with the electronic band structure calculations for the KBiI4 model compound (1.78 eV). Due to these promising optical properties, one-dimensional perovskites might be prospective absorber materials for photovoltaic applications .
|
other
| 32.16 |
Fabian et al. investigated a one-dimensional bismuth halide perovskite based on corrugated metal halide chains of distorted corner-sharing BiI6 octahedra to give BiI5 2− units, which are interlinked via dicationic alkyldiammonium species . The compound HDABiI5, with HDA = 1,6-hexanediammonium ([H3N-(CH2)6-NH3]2+), can be prepared via a solution-based method and crystallizes in an orthorhombic crystal structure [54, 187]. The optical band gap was determined to be 2.05 eV for an indirect transition. HDABiI5 was incorporated as absorber layer in meso-structured perovskite solar cells (FTO/c-TiO2/mp-TiO2/HDABiI5/Spiro-OMeTAD/Au) giving a V OC of 0.40 V, a J SC of 0.12 mA cm−2, a FF of 43%, and a PCE of 0.027% .
|
other
| 28.25 |
Two-dimensional layered structures are accommodated by metal-deficient or defect perovskites employing higher valent systems such as pnictogens, in which vacancies are present within the inorganic framework concomitant with trivalent metal cations. The crystal structure is based on a cubic close packing of A and X atoms with B-site cations occupying two-thirds of the octahedral cavities, while one-third of the remaining metal sites are vacant (K3Bi2I9 structure type). This results in the formation of inorganic metal-deficient layers of the type B2/3X4 2−, which are built up of corrugated layers of corner-sharing, distorted BX6 octahedra to give a two-dimensional structure. The structure can be, therefore, considered as distorted defect variant of the classical three-dimensional ABX3-type perovskite .
|
other
| 30.42 |
K3Bi2I9 and Rb3Bi2I9 are examples for two-dimensional layered defect perovskites. Both compounds can be prepared by solution-based or solid-state reactions, and were shown to exhibit an improved stability under ambient conditions compared to lead- and tin-based analogues . The optical band gaps were determined to be 2.1 eV for both compounds with a direct band character as predicted from electronic band structure calculations . In contrast to that, the Cs3Bi2I9 analogue with the larger A-site cation Cs+ can only adopt a zero-dimensional perovskite structure with totally different optoelectronic properties as discussed before.
|
other
| 31.03 |
However, recently Johansson et al. reported on a layered perovskite structure for CsBi3I10, which was prepared via a solution-based processing method by adjusting the stoichiometric composition of the starting materials CsI and BiI3 . CsBi3I10 features a layered structure similar to BiI3 alternating with zero-dimensional structures as found in Cs3Bi2I9. CsBi3I10 exhibits a band gap of 1.77 eV similar to BiI3 and an absorption coefficient of 1.4 × 105 cm−1, which is comparable to lead-based analogues [169, 188]. In comparison to the zero-dimensional Cs3Bi2I9 compound (2.03 eV), the layered CsBi3I10 has a lower band gap, which results in improved light-harvesting properties. In addition, CsBi3I10 shows improved film formation properties compared to Cs3Bi2I9 with more uniform, smoother and pinhole-free layers, which is advantageous for photovoltaic applications. CsBi3I10 was implemented as absorber material in meso-structured solar cells (FTO/c-TiO2/mp-TiO2/perovskite/P3HT/Ag) yielding a PCE of 0.40%, which is significantly higher compared to the Cs3Bi2I9 (0.02%) and BiI3 (0.07%) solar cells obtained in the same device architecture but significant lower compared to the Cs3Bi2I9-based solar cells obtained by Park et al. (PCE of 1.09%) .
|
study
| 29.47 |
Another example for a two-dimensional layered perovskite structure is (NH4)3Bi2I9 [48, 189]. (NH4)3Bi2I9 crystallizes in a monoclinic crystal system and has a similar structure as the Rb and K analogues discussed above. Hydrogen bonding interactions of the type N–H···I were found to be essential for the stabilization of the layered structure . Besides the low-temperature solution processability, (NH4)3Bi2I9 has an optical band gap of 2.04 eV, which is comparable to the band gaps of the above-discussed Rb and K analogues (2.1 eV). A further example for a layered perovskite structure is the metal-deficient (H2AEQT)B2/3I4 (B = Sb, Bi) perovskite, where AEQT is 5,5′′′-bis-(aminoethyl)-2,2′:5′,2′′:5′′,2′′′-quaterthiophene . However, both (NH4)3Bi2I9 and (H2AEQT)B2/3I4 have not been used as absorber material for photovoltaic applications so far.
|
other
| 31.39 |
Three-dimensional perovskite structures containing bismuth have only been obtained in quaternary double perovskites with a basic formula unit of A2BIBIIX6 [16, 58, 60, 150] by heterovalent substitution of Pb2+ by a combination of a monovalent Bi+ (BI) and a trivalent Bi3+ (BII) cation. The double perovskite structure (elpasolite) is based on corner-sharing BIX6 and BIIX6 octahedra alternating along the three crystallographic axes in a rock-salt ordered cubic structure to form a three-dimensional network with mono- and trivalent metal ions occupying the BI and BII sites, respectively [16, 63, 64, 190]. The cuboctahedral cavities within this elpasolite structure are occupied by A-site cations such as Cs+ or CH3NH3 + (Fig. 15) [16, 190, 191].Fig. 15 a Crystal structure of rock-salt ordered double halide perovskites (turquoise: monovalent A-site cation, gray monovalent BI cation, orange trivalent BII cation, brown halide counterion). b Face-centered cubic sublattice in double halide perovskites comprising edge-sharing tetrahedral positions. Adapted with permission from . Copyright (2016) American Chemical Society
|
study
| 33.9 |
a Crystal structure of rock-salt ordered double halide perovskites (turquoise: monovalent A-site cation, gray monovalent BI cation, orange trivalent BII cation, brown halide counterion). b Face-centered cubic sublattice in double halide perovskites comprising edge-sharing tetrahedral positions. Adapted with permission from . Copyright (2016) American Chemical Society
|
study
| 35.12 |
Such quaternary halide double perovskite structures can be found for mixed-valent perovskite systems based on thallium (e.g. Cs2Tl+Tl3+X6 (X = F, Cl) ) and gold (e.g. Cs2Au+Au3+I6 ) as well. Other examples of halide double perovskites are based on monovalent alkali metal (e.g. Na+) and noble-metal (e.g. Cu+, Ag+, Au+) cations and trivalent metal ions such as group-13 elements (e.g. In3+, Tl3+), pnictogens (e.g. Sb3+, Bi3+), lanthanides (e.g. La3+, Ce3+, Pr3+, Nd3+, Sm3+, Eu3+, Gd3+, Dy3+, Er3+, Tm3+, Lu3+), and actinides (e.g. Pu3+, Am3+, Bk3+) [63, 150]. Considering bismuth-based halide double perovskites, various compounds have been investigated with regard to the synthesis and crystal structure as well as optical and electronic properties in theory and experiment [16, 63, 64, 190, 191]. Cs2AgBiX6 (X = Cl, Br) perovskites, for example, can be synthesized via a solution-based or a solid-state reaction, crystallize in the elpasolite structure, and exhibit improved stability in terms of heat and moisture under ambient conditions compared to lead-based halide perovskites [16, 64, 190]. However, Cs2AgBiBr6 was still found to degrade upon exposure to air and light over a period of weeks . Cs2AgBiCl6 and Cs2AgBiBr6, are indirect semiconductors with experimental band gaps in the range of 2.2–2.77 eV for Cs2AgBiCl6 and 1.95–2.19 eV for Cs2AgBiBr6 [16, 63, 64, 190].
|
study
| 28.95 |
The family of pnictogen-noble metal halide double perovskites is especially interesting for photovoltaic applications because of the structural similarity, i.e. three-dimensional structure, to lead-based perovskites despite the different valence of the metal cations incorporated. In addition, a huge variety of material compositions is amenable due to the high number of possible element combinations of monovalent (BI = Cu+, Ag+, Au+) and trivalent (BII = Sb3+, Bi3+) metal cations together with organic and inorganic cations (A) and halide anions (X). Based on first-principle calculations, pnictogen-noble metal halide double perovskites have low carrier effective masses, and the calculated electronic band gaps were found to be tunable in the visible range depending on the choice of the noble metal, i.e. 1.3–2.0 eV (Cs2CuBiX6), 1.6–2.7 eV (Cs2AgBiX6), and 0.5–1.6 eV (Cs2AuBiX6) .
|
other
| 30.28 |
Hybrid halide double perovskites such as (CH3NH3)2KBiCl6 incorporating organic cations have been reported recently . (CH3NH3)2KBiCl6 was prepared using a hydrothermal method through the reaction between CH3NH3Cl, KCl, and BiCl3. Theoretical calculations of the electronic structure predict an indirect character of the band gap (3.02 eV), which is in good agreement with the experimental value of 3.04 eV determined from reflectance measurements and comparable to the lead analogue CH3NH3PbCl3 (2.88 eV [191, 192]). However, no solar cell data have been reported yet.
|
other
| 30.72 |
Structural, optical as well as solar cell data of bismuth halide perovskites are summarized in Table 9.Table 9Structural and optical data of bismuth halide perovskites and the highest obtained PCEs (if applied in photovoltaic devices)PerovskiteSim./exp.Crystal system (space group)DimensionalityBand gap/eVPCE/%References(NH4)3Bi2I9 Sim./exp.Monoclinic (P21/c)2D2.04–(CH3NH3)3Bi2Br9 Exp.Trigonal (P \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\bar{3}$$\end{document}3¯ m1)–––(CH3NH3)3Bi2I9 Sim./exp.Hexagonal (P63/mmc) at 300 K0D dimer1.94–2.110.42[36, 175–177, 180, 182–184, 193]Monoclinic (C2/c) at 160 K2.04[180, 181]Monoclinic (P21) at 100 K–(CH3NH3)3Bi2I9−xClx Exp.Hexagonal (P63/mmc)–2.40.003(C6H14N)3Bi2I9 Sim./exp.Monoclinic (Pc)0D dimer2.9–K3Bi2I9 Sim./exp.Monoclinic (P21/n)2D2.1–Rb3Bi2Br9 Exp.Orthorhombic (Pnma)–2.62–Rb3Bi2I9 Sim./exp.Monoclinic (Pc)2D1.89–2.1–Monoclinic (P21/n)Cs3Bi2Br9 Exp.Trigonal (P \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\bar{3}$$\end{document}3¯ m1)2D2.50–Cs3Bi2I9 Sim./exp.Hexagonal (P63/mmc)0D dimer1.8–2.21.09[16, 36, 66, 162, 164](CH3NH3)2KBiCl6 Sim./exp.Trigonal (R \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\bar{3}$$\end{document}3¯ m)3D3.04–Cs2CuBiX6 (X = Cl, Br, I)Sim.Cubic (Fm \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\bar{3}$$\end{document}3¯ m)3D2.0 (X = Cl)–1.9 (X = Br)1.3 (X = I)Cs2AgBiCl6 Sim./exp.Cubic (Fm \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\bar{3}$$\end{document}3¯ m)3D2.2–2.77–[16, 63, 190]Cs2AgBiBr6 Sim./exp.Cubic (Fm \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\bar{3}$$\end{document}3¯ m)3D1.95–2.19–[16, 63, 64, 190]Cs2AgBiI6 Sim.Cubic (Fm \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\bar{3}$$\end{document}3¯ m)3D1.6–Cs2AuBiX6 (X = Cl, Br, I)Sim.Cubic (Fm \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\bar{3}$$\end{document}3¯ m)3D1.6 (X = Cl)–1.1 (X = Br)0.5 (X = I)LiBiI4 5 H2OExp.Monoclinic (C2/c)1D1.7–1.76–MgBi2I8·8 H2OExp.Monoclinic (P21/c)1D1.7–1.76–MnBi2I8·8 H2OExp.Monoclinic (P21/c)1D1.7–1.76–KBiI4·H2OExp.Monoclinic (P21/n)1D1.7–1.76–HDABiI5 Exp.Orthorhombic1D2.050.027[54, 187][C(NH2)3]3Bi2I9 Exp.Orthorhombic (Cmcm)–––(C10H7NH3)BiI4 Exp.Orthorhombic (Pbca)1D2.32–[C6H4(NH3)2]2Bi2I10·4 H2OExp.Monoclinic (P21/n)0D2.84–(H2AEQT)Bi2/3I4 Exp.Monoclinic (C2/m)2D––CsBi3I10 Exp.–2D1.770.40
|
clinical case
| 29.39 |
Tellurium is a group-16 element with relatively low abundance in the Earth’s crust. There are various aspects that suggest tellurium as potential heterovalent replacement candidate for lead in the perovskite structure. The tetravalent Te4+ cation (1) is isoelectronic to Sn2+ (4d10 5s2) and has a similar s2 valence electronic configuration as the divalent Pb2+ featuring a 5s2 lone pair, (2) has a comparable electronegativity (Te: 2.1, Sn: 1.96, Pb: 2.33) but (3) a slightly smaller ionic radius (97 pm) compared to the divalent Sn2+ (110 pm) and Pb2+ (119 pm) metal cations [51, 125].
|
study
| 28.05 |
In a first approach, the split-anion method is based on the partial substitution of halide with chalcogenide anions in ABX3-type metal halide perovskites forming mixed chalcogenide-halide perovskites with a general formula AB(Ch,X)3 . Due to the more covalent bonding character of metal–chalcogenide bonds compared to metal halide bonds, mixed chalcogenide-halide compounds are proposed to exhibit an enhanced stability under ambient atmosphere .
|
other
| 30.42 |
Sun et al. theoretically investigated the potential of the split-anion approach for bismuth-based perovskites using first-principles calculations . The halogen anions (X = Cl, Br, I) are partially substituted with chalcogenides (Ch = S, Se, Te), i.e. one per formula unit, to obtain I–III–VI–VII2-type semiconductors with the formula CH3NH3BiChX2 exhibiting calculated direct band gaps in the range of 1.24–2.00 eV (Fig. 16). CH3NH3BiSeI2 and CH3NH3BiSI2, in particular, were identified as promising absorber materials with direct band gaps of 1.3 and 1.4 eV, respectively .Fig. 16 a Atomic structures of CH3NH3PbI3 and CH3NH3BiSeI2, and schematic representation of the split-anion approach for the replacement of Pb in CH3NH3PbI3; b Calculated band gaps of CH3NH3BiXY2 (X = S, Se, Te; Y = Cl, Br, I) using HSE functional with spin–orbit coupling. The dashed line indicates the optimal band gap for single-junction solar cells according to the Shockley–Queisser theory. Adapted with permission from . Copyright (2016) Royal Society of Chemistry
|
study
| 30.44 |
Tellurium halide perovskites with the general formula A2TeX6 employing ammonia (NH4 +), alkali metal cations (K+, Rb+, Cs+), and thallium (Tl+) as A-site cation and halide counterions (Cl−, Br−, I−) were investigated with regard to crystal structure, optical and other physicochemical properties [162, 196]. The inorganic tellurium iodide perovskites A2TeI6 (A = K, Rb, Cs, Tl) are especially interesting for photovoltaic applications due to the low band gaps in the range of 1.38–1.52 eV . Cs2TeI6, for example, was investigated by Maughan et al. . The crystal structure of this compound is derived from the three-dimensional double perovskite structure (A2BIBIIX6). While one B-site (BI) is accommodated by the tetravalent tellurium cation, the other one (BII) is replaced with a vacancy forming a vacancy-ordered cubic double perovskite of the type A2BX6 (K2PtCl6 structure type), in which discrete BX6 2− octahedra are interconnected by monovalent A-site cations occupying the cuboctahedral voids . Electronic band structure calculations indicate an indirect band gap. The experimental band gap was determined to be between 1.52 and 1.59 eV [96, 162]. A summary of structural and optical data of tellurium halide perovskites is given in Table 10. However, to the best of our knowledge, tellurium-based perovskites have not been examined as alternative lead-free absorber material for photovoltaics.Table 10Structural and optical data of tellurium halide perovskites. Dimensionalities and PCE values have not been reportedPerovskiteSim./exp.Crystal system (space group)Band gap/eVReferences(NH4)2TeCl6 Exp.Cubic (Fm \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\bar{3}$$\end{document}3¯ m)–K2TeCl6 Exp.Monoclinic (P21/n)–Rb2TeCl6 Exp.Cubic (Fm \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\bar{3}$$\end{document}3¯ m)–Cs2TeCl6 Exp.Cubic (Fm \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\bar{3}$$\end{document}3¯ m)–(NH4)2TeBr6 Exp.Cubic (Fm \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\bar{3}$$\end{document}3¯ m)–K2TeBr6 Exp.Monoclinic (P21/c)2.17[162, 196]Rb2TeBr6 Exp.Cubic (Fm \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\bar{3}$$\end{document}3¯ m)2.19Cs2TeBr6 Exp.Cubic (Fm \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\bar{3}$$\end{document}3¯ m)2.20Tl2TeBr6 Exp.Tetragonal (P4/mnc)2.06(NH4)2TeI6 Exp.Monoclinic (P21/n)–K2TeI6 Exp.Monoclinic (P21/c)1.38Rb2TeI6 Exp.Tetragonal (P4/mnc)1.43[162, 196]Cs2TeI6 Exp.Cubic (Fm \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\bar{3}$$\end{document}3¯ m)1.52–1.59[96, 162]Tl2TeI6 Exp.Monoclinic (P21/c)1.47
|
clinical case
| 29.05 |
Even though much progress has been made in the field of alternative lead-free perovskite semiconductors and many new absorber materials for photovoltaic applications have been proposed, these new materials have been shown to be not fully competitive in terms of efficiency and they suffer from problems such as chemical stability and toxicity, which are still not fully overcome. However, it is also possible to introduce chalcogenide anions into the perovskite structure by replacing the halides partly or fully.
|
study
| 28.9 |
a Atomic structures of CH3NH3PbI3 and CH3NH3BiSeI2, and schematic representation of the split-anion approach for the replacement of Pb in CH3NH3PbI3; b Calculated band gaps of CH3NH3BiXY2 (X = S, Se, Te; Y = Cl, Br, I) using HSE functional with spin–orbit coupling. The dashed line indicates the optimal band gap for single-junction solar cells according to the Shockley–Queisser theory. Adapted with permission from . Copyright (2016) Royal Society of Chemistry
|
study
| 37.4 |
Hong et al. investigated inorganic mixed-anion perovskites with a general AB(Ch,X)3 structure (A = Cs, Ba; B = Sb, Bi; Ch = chalcogen; X = halogen), where halogen anions are partially replaced with chalcogenide anions . According to DFT calculations, the examined perovskite materials were found to be thermodynamically unstable and to decompose into secondary phases . This instability was supported in solid-state synthesis experiments by the formation of distinct halide and chalcogenide phases or mixed-anion phases with non-perovskite structures . Sun et al. theoretically examined CsSnS2Cl as an example for an inorganic mixed-anion perovskite as prospective candidate as light absorber for photovoltaic applications . Hybrid functional calculations estimated an indirect band gap of ca. 1 eV for CsSnS2Cl in the distorted perovskite phase and predicted promising optical absorption properties even higher than for CsSnI3 .
|
study
| 28.25 |
Up to now, the mixed chalcogenide-halide approach has not yielded new absorber materials but the huge variety of possible element compositions for new I–III–VI–VII2, II–II–VI–VII2, I–IV–VI2–VII or II–III–VI2–VII semiconductors makes the split-anion approach interesting for further research.
|
other
| 30.16 |
Improved stability properties can be expected in the case of total substitution of halide with chalcogenide anions . This leads to a class of metal chalcogenide perovskite (ABCh3) semiconductors, which have already been studied back in the 1950s . Recently, this class has come into the focus as potential absorber materials for photovoltaic applications [197, 198, 200, 201].
|
study
| 29.56 |
Wang et al. extended the DFT studies to the family of metal sulfide perovskites with three-dimensional ABS3 structure to two-dimensional, layered Ruddlesden–Popper perovskite sulfides A3B2S7, where A are alkaline-earth metals and B are transition metals . Based on the layered structure, the formula can be also expressed as AS[ABS3]n (n = 2), where ABS3 perovskite units alternate with additional AS layers for every n perovskite unit. This class of materials was reported to show a semiconducting ferroelectric photovoltaic behavior, i.e. photo-generated electron–hole pairs can be separated efficiently due to a stable ferroelectric polarization, and first-principles calculations predicted direct band gaps in the range of 1.8–2.4 eV .
|
other
| 32.8 |
Various metal chalcogenide perovskites have been investigated extensively with regard to the crystal structures and physicochemical properties in the last decades [199, 203–208]. Perera et al., for example, prepared chalcogenide perovskites such as SrTiS3, CaZrS3, SrZrS3, and BaZrS3 by high-temperature sulfurization of oxide perovskite analogues with carbon disulfide . BaZrS3 and CaZrS3 exhibited direct band gaps of 1.73 and 1.90 eV, respectively, which were determined via UV–Vis and photoluminescence measurements, making them to potential absorber materials for photovoltaic applications . In addition, the band gap was shown to be widely tunable using an anion alloying approach, i.e. engineering of the composition of metal chalcogenides based on the (partial) substitution of chalcogenide anions . Using BaZrS3 as an example, the composition can be tuned systematically by partial substitution of the sulfide ion with oxygen ions under formation of transition metal oxysulfide perovskites BaZr(OxS1−x)3 exhibiting band gaps over a wide range from 1.73 eV in case of BaZrS3 to 2.87 eV for oxysulfide perovskites . Moreover, the examined transition metal chalcogenide perovskite materials showed improved chemical stability under ambient atmosphere compared to metal halide perovskite analogues, which is due to the more covalent bonding character of the metal–chalcogenide bond [198, 200]. In addition, oxidic perovskites might become interesting for photovoltaic applications in the future and some materials with suited optical properties (e.g. BiFeO3 [209–211]) have already been investigated in photovoltaic devices.
|
study
| 30.2 |
DFT calculations of metal chalcogenide perovskites (ABCh3) with group-2 alkaline-earth metal cations (A = Ca2+, Sr2+, Ba2+), tetravalent group-4 metal cations (B = Ti4+, Zr4+, Hf4+), and chalcogenide (Ch = S2−, Se2−) ions predict promising band gaps and absorption behavior for CaTiS3, BaZrS3, CaZrSe3, and CaHfSe3 in the distorted perovskite phase . For example, a direct band gap of 1.35 eV was calculated for CaZrSe3 . Figure 17 displays the calculated values for these ABCh3 perovskite assuming three different structural motifs, a distorted perovskite phase, a needle like structure and a hexagonal structure.Fig. 17Calculated band gaps of 18 ABX3 compounds in the distorted, hexagonal, and needle-like phase using HSE06 functional. The optimal band gap region for solar cells is highlighted in green, while an extended region is highlighted in light red. Adapted with permission from . Copyright (2015) American Chemical Society
|
study
| 31.33 |
Calculated band gaps of 18 ABX3 compounds in the distorted, hexagonal, and needle-like phase using HSE06 functional. The optimal band gap region for solar cells is highlighted in green, while an extended region is highlighted in light red. Adapted with permission from . Copyright (2015) American Chemical Society
|
study
| 34.88 |
Among all reported lead-free perovskite materials, tin-based perovskites have been most intensively investigated up to now and show the highest PCE values of all alternative perovskite solar cells. PCE values of approximately 6% have been obtained with CH3NH3SnI3 and CH(NH2)2SnI3. Even though the stability of tin perovskites is lower compared to lead-based perovskite absorbers, progress has been made on this topic and a lifetime test over 77 days without an efficiency decay has already been reported. This makes tin-based perovskites to very promising materials for the realization of low-cost and sustainable lead-free solar cells. Germanium halide perovskites have very similar band gaps to lead-based compounds. However, they are chemically more unstable and much less investigated than tin-based perovskites, which is maybe also the reason why the PCEs of germanium perovskite-based solar cells remained significantly lower so far.
|
study
| 34.4 |
Alkaline-earth metals such as magnesium, calcium, strontium, and barium are suitable candidates for homovalent substitution of lead in the perovskite structure due to ionic radii comparable to lead. Magnesium iodide perovskites, in particular, were shown to have a tunable band gap in the visible range (0.9–1.7 eV ). Calcium-, strontium-, and barium-based halide perovskites, however, are possibly not a good alternative to lead halide perovskite semiconductors for photovoltaic applications due to the high band gaps (2.95–3.6 eV ), and their sensitivity towards humidity .
|
study
| 27.34 |
In addition, the family of transition metal-based halide perovskites, which often feature lower dimensional structures isostructural to Ruddlesden–Popper phases arising from the smaller ionic radii of the respective transition metals, has attracted considerable attention. Copper halide perovskites, in particular, are among the most promising transition metal-based perovskites with PCEs up to 0.63% .
|
study
| 26.75 |
Antimony halide perovskites are a further emerging class of lead-free semiconductors with promising optoelectronic properties. A key aspect of antimony halide perovskites is the enormous structural diversity ranging from zero-dimensional dimer to three-dimensional elpasolite-type double halide perovskite structures, which can not only be manipulated by the nature and size of the cationic and anionic species but also by the processing methodology . For antimony-based perovskite solar cells, PCE values up to 0.66% are reported . However, research on this material for photovoltaic applications is still in the beginning and rapid progress in terms of performance as well as in the development of interesting alternative perovskite-type semiconductors is expected.
|
study
| 29.12 |
The huge structural diversity ranging from zero-dimensional up to three-dimensional structures together with tunable band gaps in the visible range makes also bismuth halide perovskites a promising alternative with PCE values already exceeding 1% . Bismuth perovskites show improved environmental stability compared to tin- or germanium-based perovskites.
|
study
| 28.27 |
Moreover, metal chalcogenide perovskite semiconductors provide a promising solution to address the limited chemical instability and the toxicity issue of lead-based systems. New strategies in materials design and band gap engineering over a wide range by tuning the stoichiometry and compositions, for example via a split-anion or an anion alloying approach to form mixed halide-chalcogenide compounds, enable the development of a remarkable number of novel absorber materials. Theoretical calculations predicting promising direct band gaps and improved optical absorption properties within the visible range compared to lead-based analogues highlight the potential of metal chalcogenide perovskite semiconductors for photovoltaics.
|
study
| 28.78 |
Patients that undergo autologous hematopoietic stem cell transplant (aHCT) for the treatment of a persistent or relapsed/refractory Hodgkin lymphoma (HL) or non-Hodgkin lymphoma (NHL) are at high risk of a secondary therapy-related myelodysplasia/acute myeloid leukemia (t-MDS/AML), which constitutes a fatal complication of aHCT [1–7]. The major risk factors for t-MDS/AML (reviewed in and ) include the cumulative dose of chemotherapeutic treatment to which individuals were exposed, especially alkylating agents and topoisomerase II inhibitors, as well as the use of high-dose total body irradiation as conditioning regimen for the aHCT [5,6,10–15].
|
study
| 30.22 |
Even among aHCT patients, the absolute risk of t-MDS/AML is still fairly low, with a measured incidence extending from 1.0% to 11.7% of patients (reviewed in ). Genetic factors could help explain why some individuals are more susceptible than others. In particular, differences related to DNA repair capacity (DRC) are expected to influence individual response and risk associated with exposure to chemotherapy during lymphoma treatment. Identifying patients at risk would be helpful in personalizing treatment course for each individual. Specific single-nucleotide polymorphisms have been linked to a higher risk of leukemogenesis after aHCT, most notably a specific polymorphism in XRCC1—a protein involved in multiple repair pathways related to its involvement in dealing with single strand breaks —where carrying the allele A at rs25487 has been associated with a 4.5-fold increase in the risk of t-MDS/AML after aHCT . Many other repair-related genes have also been connected to the risk of therapy-related secondary neoplasms [19–21]. However, for most individuals that develop t-MDS/AML, no genetic variant could be identified, showing that analyzing candidate genes involved in DNA repair has inherent limitations in identifying individuals at risk. Moreover, even when they could be identified, the functional significance of most genetic variants has not been determined in the previously published studies.
|
study
| 30.34 |
Another approach to identify individuals at risk is to measure functional DRC. DRC encompasses many cellular functions related to the maintenance of genome integrity. Both germinal and acquired changes could result in DRC variations, as they correspond to a functional assessment without assumptions regarding the underlying cause of the difference. It is generally understood that no single parameter can fully describe a person’s DRC and that analyzing DRC in multiple pathways is necessary to evaluate an individual’s repair capacity . Pathway-specific DRC can be investigated by using host-cell reactivation assays where a template is damaged in a predetermined manner prior to introduction into the cells, at which point the repair is measured through the reactivation of the expression of a specific transgene. The pathway analyzed is determined by the design of the template and the type of damage incurred [24–31]. One general method used to validate a DRC assay is to verify that one can measure differences in repair when comparing cells of healthy individuals to cells of individuals with a known repair deficiency, for example XP cells (i.e., cells from individuals with xeroderma pigmentosum, which are deficient in nucleotide excision repair). Such comparisons have been used to validate DRC assays since the first investigation of interindividual differences in repair . Hereditary repair deficiencies are indeed a form of interindividual difference in repair, but individuals carrying such DNA repair deficiencies show severe phenotypes compared to the general population, notably with increased risk of cancer at young age and accelerated aging . Most individuals who will develop cancer in their lifetime do not carry such severe deficiency, but might still show differences in DRC. Therefore, identifying interindividual risk of malignancy is more likely to involve measuring subtle differences in repair proficiency than identifying actual repair deficiencies. This requires assays capable of distinguishing consistently subtle differences in repair.
|
other
| 35.06 |
To investigate DRC in individuals that underwent aHCT as a way to evaluate risk of developing t-MDS/AML, we used a systematic approach by first considering how to best measure interindividual differences in repair in healthy individuals. There is no absolute independent way to determine if any measurement accurately represent the DRC of a given individual, but assays that do measure interindividual differences in repair should consistently identify relative differences across cell types, if they are to represent the individual’s genetically-determined DRC rather than the specific cell type investigated. For aHCT patients in our cohort, we had access to cryopreserved peripheral blood cells, giving the possibility to analyze either directly primary lymphocytes (i.e., T cells induced or not to proliferate) or lymphoblastoid cell lines [LCLs] (i.e., B cells after EBV transformation). We have shown previously that we can obtain consistent measurements of repair when starting from identical frozen aliquots for both types of samples using identical host-cell reactivation assays . LCLs constitute a quasi-infinite source of material and are a convenient model to investigate DRC for individuals, especially when several pathways are to be investigated . There are however reports of lack of correlation in DRC measurements between LCLs and primary lymphocytes [36–38], leading to doubts regarding the capacity for transformed cells to predict DRC in primary cells.
|
other
| 31.52 |
Therefore, we first compared relative differences in repair in primary lymphocytes and LCLs derived from the same healthy individuals using host-cell reactivation assays for four specific DNA repair pathways: non-homologous end joining (NHEJ), single-strand annealing (SSA), base excision repair (BER) and nucleotide excision repair (NER). We confirmed that primary lymphocytes are likely a better model to analyze interindividual DRC and then applied the finalized assays to investigate DNA repair in primary lymphocytes of lymphoma patients that were known to have later developed or not t-MDS/AML. Patient samples analyzed were cryopreserved immediately before as well as at some time point after aHCT.
|
other
| 32.03 |
Use of human blood samples from healthy volunteers and patients undergoing aHCT was approved by the City of Hope Internal Review Board: IRB protocol #98117 entitled “The Molecular Pathogenesis of Therapy-Related Myelodysplasia/Acute Myelogenous Leukemia”. Patients and healthy volunteers provided their written consent.
|
other
| 34.03 |
Peripheral blood of patients drawn before or after aHCT was prepared as to preserve all white blood cells (WBCs). The blood (30-35ml) was collected in heparin tubes and diluted in 1 volume of DPBS containing 2% heat-inactivated FBS. One volume of HESPAN Hetastarch (B Braun Medical Inc) was then added to the diluted blood to aggregate erythrocytes. After 45min of incubation, the upper phase containing WBCs was then transferred to a new tube and washed once with DPBS and once with culture medium before freezing (see below).
|
other
| 35.53 |
For all primary cell preparations (PBMCs for healthy volunteers or all WBCs for patients), cells were frozen or thawed with the same protocol. Cells from ~2–3 ml of blood were resuspended in 1ml of Iscove’s Modified Dulbecco’s Medium (IMDM) containing 20% heat-inactivated FBS and 1ml of cold freezing medium (60% IMDM, 20% DMSO, 20% heat-inactivated FBS) was added. Temperature was progressively decreased to -80°C in a Mr Frosty container (Nalgene) and tubes were transferred the next day to the vapor phase of a liquid nitrogen storage tank.
|
other
| 31.78 |
We have constructed a prospective cohort of patients undergoing aHCT for HL or NHL. Patients were followed longitudinally with collection of peripheral blood samples prior to aHCT, and serial peripheral blood samples until 5 years post-aHCT. This design allowed use of a nested case-control approach to compare DNA repair from “cases” that developed t-MDS/AML after aHCT with “controls” who did not develop t-MDS/AML after a period of follow-up that matched that of the corresponding index case. The matching criteria for control selection included underlying disease (HL or NHL), age at aHCT, race/ethnicity, and length of follow-up after aHCT (period of follow-up for the controls exceeded that of the patient cases under consideration). The selected individuals (Table 1) were analyzed for DRC before aHCT and at one time point afterwards, but prior to any t-MDS/AML diagnosis (S1 Fig). Repair data could not be obtained for every individual, time-point and/or every pathway, based on limited availability and/or the quality of the samples. The number of individuals included is indicated for each analysis. Five additional “control” patients were included in some analyses where cases/controls matching were not relevant (comparison pre vs post-aHCT for the same individual or comparison of patients to healthy individuals).
|
other
| 31.77 |
To investigate DNA repair capacity in healthy individuals, blood samples (30-35ml in heparin tubes) were obtained from 16 healthy volunteers (numbered H33 to 48) and processed within 3h after being drawn. The blood was first diluted in 1 volume of Dulbecco's phosphate-buffered saline (DPBS) containing 2% heat-inactivated fetal bovine serum (FBS). The diluted blood was then transferred onto a SepMate-50 tube (Stem Cell Technologies) containing 15ml of HistoPAQUE-1077 (Sigma) or Lymphoprep (Stem Cell Technologies) and further processed as recommended by the tube manufacturer before freezing (see below).
|
other
| 35.94 |
For thawing, 30ml of IMDM (with 20% FBS) containing 4,000U/ml heparin and 62.5μg/ml DNase were added dropwise to a rapidly thawed aliquot and cells were allowed to recover for at least 2h in a 37°C incubator before a 15min spin at 200g and resuspension in RPMI 1640 medium containing 10% heat-inactivated FBS.
|
other
| 36.7 |
EBV transformation of 16 healthy individuals’ B cells into LCLs (S1 Fig) was performed as previously described . Briefly, 1ml of EBV stock (supernatant prepared from B95-8 cells) was added to freshly thawed PBMCs (from 2-3ml of blood) resuspended in 2ml of culture medium (RPMI 1640 with 20% heat-inactivated FBS) containing 300μl of 100μg/ml PHA-P (Sigma). Cells were put in culture in a T25 flask and culture medium was refreshed twice a week, the volume being increased progressively based on cell density in the flask. LCLs used for repair experiments were frozen at a time point where they demonstrated their ability to grow after a freezing test (3–5 weeks post-infection in most cases). Freezing medium was 90% heat-inactivated FBS + 10% DMSO.
|
other
| 32.06 |
When indicated, T lymphocytes were purified either from PBMCs or all WBCs (hetastarch) samples using Dynabeads Flowcomp human CD3 kit (Life Technologies) as recommended by the manufacturer with the following modifications (the protocol was scaled up proportionally when there were more cells in the sample). Up to 5 x 106 total cells were resuspended in 50μl of cold isolation buffer (DPBS with 2% heat-inactivated FBS and 2mM EDTA) in a 2ml tube and 2.5μl of FlowComp Human CD3 antibody were added and incubated with the cells 10min at 4°C. Excess antibody was then washed out with 500μl of isolation buffer and cells were pelleted by centrifugation at 350g for 8min at room temperature. The cell pellet was then resuspended in 130μl of isolation buffer and 10μl of prewashed FlowComp beads were added and kept in suspension in the solution for 15min at room temperature by gentle agitation using a Hula Mixer (Life Technologies). Cells bound to the beads were then recovered by adding of 130μl of isolation buffer mixed well with 2–3 up and down pipet motions and then placing the tube on a DynaMag-5 magnet (Life Technology) for 2min. While still on the magnet, all buffer (containing unbound cells) was then removed from the tube and bead-bound cells were then washed a second time with 130μl of isolation buffer before being resuspended in 150μl of the release buffer provided with the purification kit (incubation 10min under gentle agitation with Hula Mixer at room temperature). T cells released from the beads were then counted using Trypan blue and washed by adding 500μl of isolation buffer and centrifugation 350g for 8min. Cells were then resuspended in an appropriate volume of culture medium (RPMI 1640 + 10% heat-inactivated FBS). When indicated, T cells were then induced to proliferate by adding 1:1 ratio of CD3/CD28 DynaBeads human T activator (Life Technologies) and 30U/ml of human recombinant IL-2 (PreproTech) as recommended by the manufacturer. Growth culture volume for the induction of proliferation was 500μl (24-well plate) for all healthy donor samples (1.7–8.0 x 105 T cells total) or 100μl (96-well plate) for 5 x 104 T cells for patient samples.
|
other
| 31.6 |
Plasmids pSF-tdTomato-END for NHEJ repair and pSF-tdTomato-HOM for SSA repair (Fig 1A) were digested with XhoI and ApaI and complete double-digestion was verified for quality control as described previously . For all cell types investigated, DSB repair assays were performed using 400ng of either END (for NHEJ) or HOM (for SSA) linearized plasmids transfected into cells using the P3 Primary cells nucleofection kit on the 4D Nucleofector system (Lonza). Electroporations were performed using the 20μl format (strips of electrocuvettes) and the EO-115 program. Cells were then recovered in 180μl of RMPI 1640 with 10% FBS in a 96-well plate and placed in an incubator for 12h. To determine repair efficiency, cells were then resuspended in HBSS containing 0.3μg/ml DAPI and the proportion of EYFP+ cells among viable (DAPI negative) transfected cells (tdTomato+) determined using a BD LSRFortessa cell analyzer with the FACSDiva software (version 6, BD Biosciences) as described previously . NHEJ and SSA repair were analyzed in parallel and in triplicates for each sample. The number of technical replicates (separate transfections of the same cells with the same construct in the same experiment) was in some cases reduced to 1 or 2 for patient samples, based on the number of lymphocytes available.
|
other
| 34.75 |
(A) pSF-tdTomato-END (for NHEJ, left) and pSF-tdTomato-HOM (for SSA, right) plasmids used for DSB repair assays. XhoI+ApaI double-digestion (= DSB) generated in vitro is repaired by either NHEJ or SSA after transfection in cells, thereby restoring EYFP expression. The common sequence between the two overlapping halves of EYFP in the SSA template (“YF” in grey) is 350bp long. Repair is measured by the percentage of EYFP+ cells among tdTomato+ cells. (B) pM1-Luc plasmid (left) and pRL-CMV (right) plasmids. Oxidative (8-oxoG) or UV damage (pyrimidine dimers) generated in vitro on pM1-Luc plasmid impairs expression of firefly luciferase (FL) that is then restored by BER or NER, respectively, once transfected in cells. Repair is measured by the FL activity after normalization to renilla luciferase (RL) activity (transfection control) and in comparison to the undamaged FL template (100% expression) in the same cells.
|
other
| 29.38 |
BER and NER assays use the same plasmid as reporter (Fig 1B) and differ only by the nature of the damage applied to the firefly (Photinus pyralis) luciferase (FL) reporter gene that is reactivated upon repair (in the pM1-Luc plasmid). The pRL-CMV plasmid expressing the renilla (Renilla reniformis) luciferase is used as an internal control to normalize FL activity levels for transfection efficiency (see below for description of the assay).
|
other
| 34.03 |
To prepare the BER test plasmid, 250μg of pM1-Luc in a final volume of 2.5ml in 10mM NaPO4 pH 7.5 buffer was placed in a small weighing dish on ice and irradiated for 5min with a pre-warmed 150W incandescent bulb at a distance of 10.5cm in presence of 15μM methylene blue, which generated 8-oxoG damage. For the NER test plasmid, 250μg pM1-Luc in a final volume of 2.5ml in 10mM NaPO4 pH 7.5 buffer was placed in a small weighing dish on ice and irradiated with 120J/m2 with a germicidal (UVC) lamp to generate pyrimidine dimers. The irradiation time necessary to provide the UVC dose was determined based on the radiant incidence of the lamp measured that day using a UVX digital radiometer (UVP).
|
other
| 34.56 |
After exposure to DNA damage, both BER and NER plasmids were precipitated with 1/10th volume of 3M NaOAc pH 5.2 and 2.5 volumes of ice cold 100% ethanol. After a wash with 70% ethanol, DNA pellets were resuspended in 500μl H2O and the DNA concentrations verified with a Nanodrop spectrophotometer. Finally, the volume of H2O was adjusted to a final concentration of 400ng/μl. To verify the level of DNA damage present in BER and NER plasmids, we designed a method to estimate the level of inhibition of polymerase extension specifically in the coding sequence of the FL reporter gene (S2 Fig). BamHI-digested templates (site in 3’ of the end of the gene) were subjected to 5 cycles of primer extension starting from a Cy5.5 labeled CMV-F primer. The level of Cy5.5 signal at full length extension indicates the proportion of undamaged template that remains and can serve as quality control for each batch of plasmid preparation. The BER and NER plasmid batches used for this study showed 16% and 27% of residual full length extension, respectively (S2 Fig). Although this does not predict directly the level of gene expression in vivo, the damage frequency present in these plasmids is expected to result in some background expression of the undamaged FL gene once in cells, even if no repair were to occur. Beyond the opportunity for a quality control for the level of damage generated, the advantage of such a level of damage is that we can infer from these estimates that few lesions exist (1 or 2) per template. As a consequence, a limited number of discrete repair events can be expected to result in increased expression levels, making the assays sensitive to low levels of repair.
|
other
| 33.78 |
To measure DRC, 400ng of either BER or NER template were co-transfected (see nucleofection protocol in previous section) with 100ng of pRL-CMV plasmid. Pre-mixes containing this ratio of BER+pRL-CMV or NER+pRL-CMV plasmids were prepared in advance to insure consistency in co-transfected amounts, eliminating pipetting error as a source of variation between transfections. After nucleofection, cells were transferred into 180μl phenol red-free RPMI 1640 medium with 10% heat-inactivated FBS and placed in an incubator for 8h. To quantify repair by BER or NER, cells were centrifuged in the 96-well culture plate and some of the excess culture volume was removed. Finally, 75μl of resuspended cells were used to measure the firefly over renilla luciferase relative activities for each transfection, using the Dual Glo Luciferase assay system (Promega) as recommended by the manufacturer. pRL-CMV plasmid alone and undamaged pM1-Luc+pRL-CMV were used as controls for 0% and 100% firefly luciferase activity, respectively. Two (patient samples) or 3 (healthy controls) technical replicates were averaged to determine DRC, meaning separate test transfections of the same construct in the same experiment. The reproducibility among those replicates tended to be lesser in samples where more cell death was observed (analysis in patient samples and/or at time points more than 8h post-transfection).
|
other
| 36.84 |
Data obtained for all the assays are summarized (S1 File.). Pearson’s correlation was used to assess the associations between DRC in primary T cells and LCLs. Nonparametric Wilcoxon signed rank test was used to compare DNA repair between matched pairs of cancer case and cancer control before and after transplant. Nonparametric Mann-Whitney-Wilcoxon test was used to compare difference in DNA repair between cancer group and healthy controls. Multivariate linear regression was used to assess the difference between transplant patients at pre-HCT and healthy controls, adjusting for age. Detailed methods are mentioned with the corresponding results in the text, tables or figure legends. Bonferroni correction was used to adjust multiple comparisons of the different outcomes.
|
other
| 34.4 |
To determine if transformed cells (LCLs) are a good proxy for DSB repair in primary lymphocytes of the same healthy individual, repair was evaluated using host-cell reactivation assays after transfection of damaged plasmids into both cell types using the same basic protocol. DSB repair capacity by NHEJ or SSA was measured by the proportion of EYFP+ cells among transfected cells (tdTomato+), as determined by flow cytometry. EYFP expression is the result of NHEJ repair or SSA repair, depending on the design of the linearized plasmid transfected (Fig 1A).
|
review
| 28.98 |
We have shown before that NHEJ and SSA repair can be measured in non-induced lymphocytes, even when mixed with other white blood cells, as the latter can be disregarded from the flow cytometry analysis . However, many protocols investigating repair in peripheral blood lymphocytes induce cell proliferation prior to DNA repair analysis and we first wanted to determine whether or not to induce lymphocytes prior measuring NHEJ and SSA repair. We opted to induce T lymphocytes using CD3/CD28 beads (Dynabeads human T activator CD3/CD28, Invitrogen) that mimic physiological activation of T cells when recognizing a specific antigen. Such an induction is better controlled when performed on purified T (CD3+) cells with a ratio of one bead per T cell. Experiment on the effect of induction were therefore performed on purified T cells rather than PBMCs as a whole, but we have verified that DSB repair is constantly the same for a given individual whether lymphocytes were purified or not prior to repair measurements (S3 Fig). This result also confirms that repair measured directly in PBMCs with this protocol is a good representation of repair specifically in T cells and therefore that T cells are the cell type investigated in all our experiments performed on primary lymphocytes regardless of the type of sample preparation.
|
other
| 33.22 |
To determine the effect of induction on DSB repair, purified T (CD3+) cells of two healthy individuals were either analyzed non-induced or induced to proliferate for up to 9 days. Fig 2 shows a strong increase in both types of DSB repair upon induction of proliferation (Fig 2A and 2B for NHEJ and SSA, respectively), but the levels of induction greatly varied with the time-point analyzed. Such variations make it difficult to conclude which, if any, of the obtained values might best represent the individual’s DRC, as the time-point selected post-induction would tremendously influence the results for any given individual. Moreover, the effect of the induction is so strong (up to 3.5 times the non-induced value after 3 days induction) that it is likely to dwarf the effect of any existing interindividual differences in repair. As a result, we opted to use non-induced cells for DSB repair assays on primary lymphocytes of healthy individuals.
|
other
| 33.28 |
(A) NHEJ and (B) SSA repair in purified T cells of 2 healthy individuals either non-induced or induced to proliferate for 3 to 9 days (C) Correlation between SSA and NHEJ repair in non-induced unpurified lymphocytes (red triangles) and in 3–5 weeks old early LCLs (black circles). The linear regression trend lines with 95% confidence intervals are indicated, as well as the value of the slopes (a).
|
other
| 31.38 |
Repair experiments in LCLs were performed on freshly thawed, early LCLs (frozen shortly after confirmation of their transformed status ~3–5 weeks post-EBV infection). Table 2 shows that DSB repair measurements in non-induced lymphocytes of 16 individuals as compared to LCLs derived from the same individuals are positively correlated, but that correlation does not reach significance. As uninduced primary lymphocytes most closely represent cells directly from the individual investigated, they are the most likely to represent the individuals’ DRC when compared to LCLs.
|
other
| 32.66 |
In the course of measuring DSB repair in non-induced lymphocytes and LCLs, we noticed that the two DSB repair pathways seemed to vary together for each cell type. Table 3 shows that there is a significant correlation between NHEJ and SSA measurements (r = 0.708 and r = 0.807 for lymphocytes and LCLs, respectively) and Fig 2C illustrates the direct relationship between the two types of repair in both cell types. The identical slopes for the trend lines of lymphocytes and LCLs indicate that there is a pattern in the relationship between those pathways that exists systematically in cells, indicating that measurements in LCLs might be meaningful, even if the LCLs do not fully recapitulate interindividual differences in repair.
|
other
| 35.06 |
As for the previous assays, we first verified the effect of CD3/CD28-induced proliferation on BER and NER activity in purified T (CD3+) cells (Fig 3A and 3B), but found that only background levels of luciferase activity (expression due to undamaged template that is similar for all individuals–S2 Fig) could be detected without induction, and therefore that induction was necessary to investigate those repair pathways. We opted to measure BER and NER after activation performed in a controlled manner using an exact 1:1 ratio of T cells to CD3/CD28 beads, and found that we could reliably detect interindividual differences in BER and NER using these experimental conditions (3 days induced samples in Fig 3A and 3B).
|
other
| 31.17 |
(A) BER and (B) NER repair in purified T cells of 4 healthy individuals either non-induced or induced to proliferate for 3 days. Luciferase expression in non-induced samples is consistent with background expression from undamaged template (S2 Fig) (C) Correlation between BER and NER repair in T cells induced 3 days (red triangles) and in early LCLs (black circles) for 12 individuals. The linear regression trend lines with 95% confidence intervals are indicated, as well as the value of the slope (a).
|
other
| 31.22 |
Therefore we compared BER and NER in the same early LCLs as previously, and in T cells induced to proliferate for 3 days and found there was no correlation between the two cell types for those pathways either (Table 2). On the other hand, and similar to what was observed for DSB repair assays, Table 3 shows that there is a significant correlation between BER and NER measurements (r = 0.918 and r = 0.819 for lymphocytes and LCLs, respectively) and Fig 3C illustrates the direct relationship between the two types of repair measurements in each cell types. The slopes for the trend lines are similar as well, indicating that those pathways follow also a pattern in their relationship to each other in all cells analyzed.
|
other
| 34.8 |
Overall, and although there is evidence that an individual’s genetic make-up contributes to the measured repair and that there are clear patterns to repair as determined in LCLs, it seems likely that primary cells allow more accurate measurements of interindividual differences in DNA repair capacity.
|
other
| 33.1 |
For 20 aHCT recipients (13 controls and 7 cases), we could obtain DSB repair data both before and after aHCT (S1 Fig), allowing us to study whether the transplant itself had affected their DRC. We observed a significant decrease in both NHEJ and SSA after aHCT (Fig 4A) with an average decrease of 6.9% and 6.1% in repair, respectively. Most individuals showed a decrease in DSB repair (relative repair <100%) with an average post-aHCT repair equivalent to 73.8% and 76.2% of its value pre-aHCT for NHEJ and SSA, respectively (Fig 4B). Cases did not show more decrease than control individuals (data not shown) and the observed DSB repair decrease did not help predict what individuals were at risk of developing t-MDS/AML.
|
other
| 31.25 |
(A) NHEJ and SSA measured in the same 20 aHCT recipients (13 controls, 7 cases) before and after aHCT (p-value for Wilcoxon signed rank test). (B) Repair post-aHCT normalized to pre-aHCT for each patient. A value <100% indicates a decrease in NHEJ (close triangles) or SSA (open triangle) after transplant.
|
other
| 30.2 |
Our main purpose in this study was to analyze potential differences in repair in individuals that underwent aHCT, but the frozen samples we have available for patients in this cohort contain all white blood cells, not just PBMCs, as they were simply purified from red blood cells using hetastarch rather than a density gradient. We have shown previously that repair in lymphocytes can be influenced by the presence of granulocytes in their environment at the time of transfection, as is the case in hetastarch-prepared samples . Moreover, we had very limited amount of material for each lymphoma patient. Therefore, all repair analysis on patient samples were performed on purified T cells (CD3+). After purification, a limited number of cells (5 x 104 T cells) were expanded using CD3/CD28 beads and IL-2 for 3 days for BER and NER assays, whereas the rest of the purified T cells were used non-induced for DSB repair assays (work flow scheme in S4 Fig). This strategy allowed repair measurement for all 4 DNA repair pathways using a single frozen aliquot representing cells from 2–3 ml of blood.
|
other
| 33.12 |
Patients in the cohort were recruited prior to aHCT and followed for up to 5 years afterwards. Therefore, we had multiple samples available for each individual, taken at different time points during the study. We decided to analyze 1) cells drawn prior to the transplant in order to determine if DRC could help in any way predict which individuals would later develop t-MDS/AML and 2) cells drawn for the same individuals at one time point post-aHCT but prior to any malignancy diagnosis, for DRC after transplantation (S1 Fig). Cases (who later developed t-MDS/AML) were matched to paired control individuals from the same cohort based on their diagnosis, ethnicity and duration of follow up for the post-aHCT sample (Table 1). Table 4 shows the paired comparisons between cases and controls regarding their DRC for all 4 pathways. No type of repair was significantly different between cases and controls, indicating that there was no measurable deficiency in DRC specifically in aHCT patients that later developed t-MDS/AML.
|
other
| 34.38 |
In contrast to the results with NHEJ and SSA, BER and NER repair analyzed for 18 individuals (9 cases and 9 controls) was not significantly affected by aHCT. The results for NER and BER do not indicate that repair for individuals were actually identical before and after transplant, but rather that observed variations did not display a specific identifiable pattern (S5 Fig).
|
other
| 31.81 |
We wondered if a decrease in repair could be a manifestation of aging in immune system cells. To investigate if repair was affected by age, we analyzed again the repair results for healthy individuals for each type of repair pathway in function of age at blood draw (Table 5) and found that both types of DSB repair capacity are inversely correlated with age, and more specifically so for NHEJ repair (Fig 5). Based on the slope (a) of the trendline, NHEJ repair can be estimated to decrease at a rate of 0.37% per year in healthy individuals.
|
other
| 35.44 |
On the other hand, neither BER nor NER were associated with age in healthy individuals (S6 Fig). Overall, the data is consistent with DNA repair capacity in NHEJ and, to a lesser extent in SSA, being a function that decreases with age in non-induced lymphocytes. Interestingly, this relationship of DSB repair to age was not statistically significant when analyzing LCLs of the same individuals (data not shown), with a correlation of -0.415 for NHEJ (p = 0.110) and -0.094 for SSA (p = 0.730).
|
other
| 32.34 |
We wondered how pre-aHCT patients compared to our group of healthy individuals regarding their DRC. BER was lower in pre-aHCT patients as compared to healthy individuals (p = 0.0134) but NER was not (p = 0.4347). Especially the subgroup of control patients, those who never developed t-MDS/AML, showed a much lower BER capacity than healthy individuals (average 23.3% and 39.5%, respectively–p = 0.0013) (Fig 6). After adjustment for age at aHCT, NHEJ repair in patients was marginally higher than in healthy individuals (p = 0.0149), but SSA repair was not (p = 0.4287). Interestingly, although patient samples post-aHCT followed the same patterns identified for healthy individuals (Table 3), with a correlation between NHEJ and SSA (r = 0.676, p = 0.0003) on the one hand and between BER and NER on the other hand (r = 0.478, p = 0.012), pre-aHCT patients did not show the correlation between NHEJ and SSA, which was mostly lost (p = 0.345, p = 0.161). Moreover, and unlike in healthy individuals, neither NHEJ nor SSA in pre-aHCT patients displayed any relationship to the person’s age at time of aHCT (r = 0.004, p = 0.985 and r = -0.253, p = 0.186, respectively–Table 5). Overall, these results indicate that pre-aHCT DRC measurements have features that are not consistent with those observed for other samples, including repair for the same individuals after transplantation.
|
other
| 32.2 |
It is likely that differences in DRC influence an individual’s risk of t-MDS/AML after aHCT. Being able to measure DRC might therefore help in predicting who is at higher risk and how to adapt their treatment accordingly. DRC in peripheral blood cells can be investigated directly in primary (mostly T) lymphocytes, or in LCLs after EBV transformation. Before deciding which cell model to use for measuring DRC in aHCT patients, we first investigated what seemed the most reliable way to determine an individual’s DRC using samples obtained from healthy individuals.
|
other
| 35.2 |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.