Interfacial electronic and defect engineering coupling of S-scheme CsSnBr3/SnSx (x=1, 2) heterostructures with carrier dynamics for solar cells

Exploring semiconductor perovskite materials for converting solar energy into electricity is of great significance. Recently, lead-free halide perovskite (CsSnBr3) has garnered extensive attention as a solar cell material due to its unique electronic structure and remarkable optoelectronic properties. In this work, the photovoltaic performance and carrier dynamics of S-scheme CsSnBr3/SnSx(x = 1, 2) heterostructures without and with atomic doping and bromine vacancies are investigated using density functional theory (DFT). The calculated results suggest that strong coupling and hybridization of interfacial electronic states in the CsSnBr3/SnS heterostructure lead to a narrowing of the band gap, resulting in enhanced optical absorption. Excitingly, bromine vacancies play a dual role of providing rich electrons and suppressing electron-hole pair recombination. The interfacial carrier recombination time is 1.41 ps, significantly shorter than the electron (hole) transfer time of 30.01 ps (20.81 ps), extending the carrier lifetime of the V-Br(6.3%)-CsSnBr3/SnS heterostructure. Finally, the V-Br(6.3%)-CsSnBr3/SnS-based solar cell device exhibits a higher power conversion efficiency (26.58%) compared to V-Br(3.7%)-CsSnBr3/SnS2 (25%) and a suitable open circuit voltage (1.57 V). This study presents an effective strategy for designing highly efficient CsSnBr3-based perovskite solar cells.