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 - 2018/9/24
Y1 - 2018/9/24
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 AI2BB′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 AI2BB′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.
UR - https://doi.org/10.1002/ange.201807421
U2 - 10.1002/ange.201807421
DO - 10.1002/ange.201807421
M3 - Article
VL - 130
SP - 12947
EP - 12952
JO - Angewandte Chemie
JF - Angewandte Chemie
SN - 0044-8249
IS - 39
ER -