Performance limiting defect stabilization by orbital hybridization in perovskite/C60 based solar cells

Abstract

Metal halide perovskites have emerged as promising materials for solar cells, with efficiencies close to silicon. However, trap-assisted nonradiative recombination remains one of the limiting factors, particularly at the interface with the electron transport layer, which employs fullerenes such as C₆₀. In this work, surface defects of tetragonal CH₃NH₃PbI₃ (MAPbI₃) are investigated in the presence of C₆₀, using hybrid density functional theory (DFT). We found that the presence of C₆₀ on the MAPbI₃ surface reduces the defect formation energies of certain defects and thereby increases the defect density, in line with previous experimental work [J. Warby et al., Advanced Energy Materials, 2022, 12, 2103567]. Further investigations attribute these results to a hybridization between defects and C₆₀ orbitals. This leads to a new understanding of this particular interface and highlights possible strategies to circumvent performance limitations in future perovskite solar cells.