Computational Screening of 2D All‐Inorganic Lead‐Free Halide Perovskites A<sub>3</sub>B<sub>2</sub>X<sub>9</sub> for Photovoltaic and Photocatalytic Applications
Qingyuan Luo, Liqin Su, Yanan Lu, Linghui Fang, Haibo Shu, Dan Cao, Xiaoshuang Chen
Abstract
Abstract Exploration of low‐dimensional Pb‐free halide perovskites with high stability and outstanding properties is still a pursuing target for developing integrated optoelectronic devices. Herein, comprehensive computational screening of a new class of two‐dimensional (2D) all‐inorganic Pb‐free A 3 B 2 X 9 perovskites is performed based on the first‐principles calculations. The results indicate that the structural and electronic properties of 2D A 3 B 2 X 9 structures strongly depend on the B‐X bonding interactions, which makes that their thermodynamic stability follows the trend of A 3 Bi 2 X 9 ≈A 3 Sb 2 X 9 >A 3 In 2 X 9 >A 3 Ga 2 X 9 and their interlayer interactions show a reversal trend. Owing to the lack of lone‐pair electron effect, A 3 In 2 X 9 indicate direct bandgap characteristics and present the relatively smaller bandgaps and higher electron mobilities than A 3 Sb 2 X 9 and A 3 Bi 2 X 9 . Benefit from optimal bandgaps (0.8–2.1 eV) and large absorption coefficients (10 4 –10 5 cm −1 ) in the visible region, A 3 B 2 I 9 (B = In, Sb, Bi) exhibit high power conversion efficiency up to 18.2%. Moreover, A 3 B 2 I 9 (B = Sb, Bi) is verified as efficient photocatalysts for overall water splitting. The theoretical solar‐to‐hydrogen efficiency of Rb 3 Bi 2 I 9 and Cs 3 Bi 2 I 9 are >16%. This work suggests huge potential of 2D A 3 B 2 X 9 perovskites for photovoltaic and photocatalytic applications.