Theoretical and experimental study of earth-abundant solar cell materials

In this paper, we present theoretical and experimental studies of two representative earth-abundant, thin-film solar cell materials: Cu₂ZnSnS₄ and CH₃NH₃PbI₃. Using first-principles density-functional theory, we show that both Cu₂ZnSnS₄ and CH₃NH₃PbI₃ exhibit electronic and optical properties that are suitable for solar cell applications. However, the defect physics are rather different in these two earth-abundant solar cell materials: the dominant defects produce deep gap states in Cu₂ZnSnS₄ but only shallow states in CH₃NH₃PbI₃, indicating that CH₃NH₃PbI₃ is a more promising candidate for achieving high efficiency solar cells. Through the synthesis and characterization of Cu₂ZnSnS₄ and CH₃NH₃PbI₃-based thin-film solar cells, we show that CH₃NH₃PbI₃-based thin-film solar cells exhibit significantly higher performance than Cu₂ZnSnS₄-based solar cells.