Hierarchical computational screening of layered lead-free metal halide perovskites for optoelectronic applications

Abstract

Vertically stacked layered metal halide perovskites (MHPs) have emerged as promising semiconductors for optoelectronic applications due to their low cost, tunable band gaps, and excellent stability and solution processability. However, it is still a challenge to find potential layered MHPs with both high stability and superior optoelectronic properties. Herein, we employ a hierarchical screening method to search for layered lead-free MHPs based on density functional theory calculations. This method leads to a sequential screening of MHPs from their bulks, nanosheets, to layered structures, aiming to solve the problem of lead toxicity and balance the stability and optoelectronic performance. After a series of screenings, Dion–Jacobson phase (CH₂)₈(NH₃)₂Cs_n−1Sn_nBr_3n+1 compounds are predicted as a class of layered lead-free perovskites with high stability, appropriate band gaps, and small carrier effective masses. Furthermore, an improved model is proposed to predict the maximum power conversion efficiency (PCE) of these layered perovskites. Owing to the optimal band gaps and large absorption coefficient in the visible region, Dion–Jacobson phase perovskites exhibit high PCE (>20%) when the layer number of SnBr₆ octahedrons is beyond 2, suggesting their huge potential for photovoltaic and optoelectronic devices.