Electronic Structure, Optical Transitions, and Transport Properties of Thiocyanate-Substituted α-FAPbI3 Perovskite Analogues

Hybrid perovskites have emerged as the most promising photovoltaic materials due to their excellent optoelectronic properties. However, their poor intrinsic stability is still the major issue that needs to be solved. In the past few years, incorporation of a pseudohalogen in perovskites has been proved to significantly improve the stability of hybrid perovskites. In order to analyze the effect of pseudohalogen incorporation on optoelectronic properties of FABX(3) (B = Pb2+, Sn2+; X = I-, Br-, and Cl-), we performed first-principles calculations on electronic, optical, and carrier properties of FABX(3) and thiocyanate (SCN-) substituted FABX(2)(SCN) based on the density functional theory. We found that the incorporation of SCN- in FABX(3) can tune the band gaps, effective masses, and optical properties. Moreover, the incorporation of SCN- in FABX(3 )can result in a reduced radiative recombination and enhanced transport properties due to the formation of a split-split indirect band gap. Particularly, lead-free FASnI(2)(SCN) shows superior properties for photovoltaic applications.