Effect of partial cation substitution on optoelectronic properties and ion diffusion behavior of inorganic lead halide perovskite: A theoretical investigation

Cation substitution is a widely utilized approach for tailoring the properties of lead halide perovskites. A comprehensive understanding of the impact of various cation substitutions on optoelectronic properties and ion diffusion behavior is crucial for enhancing the performance of halide perovskite materials. In this study, we constructed various double halide perovskites by cation substitution and investigated their optoelectronic properties and ion diffusion behavior through first-principles calculations. Our findings reveal that the A-site substitution with alkali cation Rb does not significantly influence the optoelectronic properties of lead halide perovskites. However, it will boost the halide migration due to the enlarged migration bottleneck. The B-site substitution with alkali earth element Sr significantly suppresses the halide migration; while the material will be no longer suitable for visible light absorption due to the enlarged bandgap. The substitution of Pb with d-orbital fulfilled Zn can also suppress the halide migration, but it will give rise to an indirect bandgap and hence affect the optoelectronic performance. The substitution of Pb with Sn can enhance both the thermostability and optoelectronic performance owing to the smaller ionic radius and similar ns2-containing electronic configuration. The increased migration barrier indicates that ion diffusion is also inhibited in double perovskite Cs2SnPbI6. Our results imply that the optoelectronic properties can be further optimized by tuning the ratio of Sn/Pb or the thickness of the perovskite layer in photovoltaic device. These results would be useful guide for the development of novel lead-less optoelectronic perovskite materials.