Hierarchical Computational Screening of Layered Lead-Free Metal Halide Perovskites for Optoelectronic Applications

Vertically stacking 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 for finding potential layered MHPs with both the high stability and superior optoelectronic properties. Herein, we report a hierarchical progressive screening method to search 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)2Csn-1SnnBr3n+1 are predicted as a class of these layered lead-free perovskites with high stability, proper band gaps, and small carrier effective masses. Furthermore, an improved model is proposed to predict maximum power conversion efficiency (PCE) of these layered perovskites. Owing to 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.