Theoretical study of the strain influence on lead-free bismuth-based halide perovskites

The existence of bio-accumulative lead hinders the commercialization of optoelectronic applications of Pb-based halide perovskites (PVKs). Therefore, researchers are seeking for comparative lead-free PVKs. Owing to the identical electronic configuration with Pb, Bi-based PVKs are proved to be one of the most promising candidates. Because strain is widely existed altering materials’ characteristics, it is crucial to study the influences of strain on the Bi-based PVKs. Our theoretical work investigates the strain influences on two kinds of Bi-based PVKs, i.e., Cs3Bi2Br9, and Cs2BiAgBr6. It is observed that both the tensile and compressive strains effectively change the crystal structures and the bandgaps, i.e., enlargement under tensile strain while shrinkage under compressive strain. Simultanously, the absorption spectra of these PVKs are also discussed. The strain study of Bi-based PVKs will offer guidance to the further development of lead-free PVKs.