TY - JOUR
T1 - Small-Band-Gap Halide Double Perovskites
AU - Slavney, Adam H.
AU - Leppert, Linn
AU - Saldivar Valdes, Abraham
AU - Bartesaghi, Davide
AU - Savenije, Tom J.
AU - Neaton, Jeffrey B.
AU - Karunadasa, Hemamala I.
PY - 2018
Y1 - 2018
N2 - Despite their compositional versatility, most halide double perovskites feature large band gaps. Herein, we describe a strategy for achieving small band gaps in this family of materials. The new double perovskites Cs2AgTlX6 (X=Cl (1) and Br (2)) have direct band gaps of 2.0 and 0.95 eV, respectively, which are approximately 1 eV lower than those of analogous perovskites. To our knowledge, compound 2 displays the lowest band gap for any known halide perovskite. Unlike in AIBIIX3 perovskites, the band-gap transition in AI
2BB′X6 double perovskites can show substantial metal-to-metal charge-transfer character. This band-edge orbital composition is used to achieve small band gaps through the selection of energetically aligned B- and B′-site metal frontier orbitals. Calculations reveal a shallow, symmetry-forbidden region at the band edges for 1, which results in long (μs) microwave conductivity lifetimes. We further describe a facile self-doping reaction in 2 through Br2 loss at ambient conditions.
AB - Despite their compositional versatility, most halide double perovskites feature large band gaps. Herein, we describe a strategy for achieving small band gaps in this family of materials. The new double perovskites Cs2AgTlX6 (X=Cl (1) and Br (2)) have direct band gaps of 2.0 and 0.95 eV, respectively, which are approximately 1 eV lower than those of analogous perovskites. To our knowledge, compound 2 displays the lowest band gap for any known halide perovskite. Unlike in AIBIIX3 perovskites, the band-gap transition in AI
2BB′X6 double perovskites can show substantial metal-to-metal charge-transfer character. This band-edge orbital composition is used to achieve small band gaps through the selection of energetically aligned B- and B′-site metal frontier orbitals. Calculations reveal a shallow, symmetry-forbidden region at the band edges for 1, which results in long (μs) microwave conductivity lifetimes. We further describe a facile self-doping reaction in 2 through Br2 loss at ambient conditions.
KW - absorber
KW - band gap
KW - band structure
KW - doping
KW - halide double perovskite
UR - http://www.scopus.com/inward/record.url?scp=85053282686&partnerID=8YFLogxK
U2 - 10.1002/anie.201807421
DO - 10.1002/anie.201807421
M3 - Article
AN - SCOPUS:85053282686
SN - 1433-7851
VL - 57
SP - 12765
EP - 12770
JO - Angewandte Chemie - International Edition
JF - Angewandte Chemie - International Edition
ER -