Interfacial electronic and vacancy defect engineering coupling of the Z-scheme CsSnBr3/SnS2 heterostructure for photovoltaic performance: a hybrid DFT study

Abstract

The photoelectric conversion efficiency of CsSnBr₃ solar cells only reached 3.04% due to the insufficient separation of photogenerated charge and the short lifetime of the carriers. Herein, interfacial electronic properties and photovoltaic performance of the CsSnBr₃/SnS₂ heterostructure without and with Bromine vacancy defects are studied using a hybrid density functional method. We find that strong coupling and hybridization of interfacial electronic states in the CsSnBr₃/SnS₂ heterostructure can lead to a narrowing band gap, which induces excellent optical absorption. Bromine vacancies are introduced into the CsSnBr₃/SnS₂ heterostructure to provide more electrons and modulate its physicochemical properties. Excitingly, the charge transfer forms a stronger built-in electric field in the V_Br-CsSnBr₃/SnS₂ heterostructure, which can effectively promote the charge transfer between V_Br-CsSnBr₃ (001) and the SnS₂ monolayer complying with a Z-scheme pathway. The coupling interface and vacancy defects improve the photovoltaic performance of CsSnBr₃. This study offers a novel design idea for CsSnBr₃-based perovskite materials in photovoltaic applications.