Computational Screening of 2D All‐Inorganic Lead‐Free Halide Perovskites A₃B₂X₉ for Photovoltaic and Photocatalytic Applications

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 A3B2X9 perovskites is performed based on the first‐principles calculations. The results indicate that the structural and electronic properties of 2D A3B2X9 structures strongly depend on the B‐X bonding interactions, which makes that their thermodynamic stability follows the trend of A3Bi2X9≈A3Sb2X9>A3In2X9>A3Ga2X9 and their interlayer interactions show a reversal trend. Owing to the lack of lone‐pair electron effect, A3In2X9 indicate direct bandgap characteristics and present the relatively smaller bandgaps and higher electron mobilities than A3Sb2X9 and A3Bi2X9. Benefit from optimal bandgaps (0.8–2.1 eV) and large absorption coefficients (104–105 cm−1) in the visible region, A3B2I9 (B = In, Sb, Bi) exhibit high power conversion efficiency up to 18.2%. Moreover, A3B2I9 (B = Sb, Bi) is verified as efficient photocatalysts for overall water splitting. The theoretical solar‐to‐hydrogen efficiency of Rb3Bi2I9 and Cs3Bi2I9 are >16%. This work suggests huge potential of 2D A3B2X9 perovskites for photovoltaic and photocatalytic applications.