Optoelectronic and transport properties of layer-dependent two-dimensional perovskite Cs3Bi2I9

The emergence of two-dimensional (2D) perovskite provides an ideal platform for designing and fabricating microelectronic and optoelectronic devices. Here, we present detailed ab initio calculations to comprehensively explore the layer-dependent optoelectronic and transport properties of the newly synthesized 2D perovskite Cs₃Bi₂I₉. The calculations reveal that the indirect band gap of monolayer, bilayer, and trilayer Cs₃Bi₂I₉ decreases from 2.41 to 2.35 eV The charge carriers of few-layered perovskite Cs₃Bi₂I₉ are dominated by electrons, and the highest electron and hole carrier mobilities are 140 and 62 cm²V⁻¹s⁻¹ along the b axis for bilayer Cs₃Bi₂I₉. Exciton binding energies decrease from 2.48 to 1.19 eV with an increment of layer, and the calculated exciton level drops down into the valence band to generate potential exciton insulator. 2D Cs₃Bi₂I₉ exhibits potential in the field of ultraviolet detection and photoluminescent devices due to large exciton energy and ultraviolet absorption.