Advanced Technology and Manufacturing Institute (ATAMI)

Current cadmium telluride and copper indium gallium diselenide thin-film solar cells (TFSCs) utilize thick absorbers (2 - 4 μm). For efficient carrier extraction in these TFSCs, the absorber layer requires high carrier mobilities and a long minority carrier lifetime, which necessitates the use of a high purity, defect-free thin film. Developing new materials with absorption strengths stronger than those of current materials allows an ultra-thin (<1 μm) absorber to be incorporated in a drift-based TFSC. Device simulation indicates that a built-in drift field aids carrier extraction, reducing mobility and lifetime requirements. Iron- and copper-based materials are investigated within the context of ultra-thin absorbers. FeS₂ is unstable due to the formation of deleterious, low band-gap phases while Fe₂GeS₄ and CuSbS₂ exhibit a sluggish, non-abrupt onset of absorption, limiting their application in an ultra-thin drift-based TFSC. Cu₃SbS₄ exhibits desirable optical and electrical properties with a simulated TSFC efficiency of 19% for a 750 nm thick absorber layer. A new tetrahedrite-based absorber, Cu₁₀Zn₂Sb₄Se₁₃ demonstrates exceptionally strong absorption, with a simulated TSFC efficiency of 21% for a 250 nm thick absorber, indicating that Cu3SbS₄ and Cu₁₀Zn₂Sb₄Se₁₃ have potential for high efficiency drift-based TFSC applications.