DFT insights into the effects of substitutionally doped Sb defects in CuIn(S,Se)₂ solar cell absorber

Abstract

Metal chalcogenide-based semiconductors are gaining attention for optoelectronic applications like thin-film photovoltaics (PV). Sb dopant incorporation in CuIn(S,Se)2 (CISSe) solar cell has been proven to significantly enhance PV performance, as demonstrated in our previous experimental work. However, the underlying mechanisms behind this improvement remained unclear. In this study, we report on the influence of substitutionally doped Sb defect on the structural, formation energy, band structure, and optical absorption properties in CISSe, employing the hybrid HSE06 functional within the density functional theory framework. We find that the Sb prefers to substitute at In site, resulting in the most stable Sb-doped CISSe structure. Under cation-poor growth conditions, Sb prefers to substitute on In sites, while under anion-poor growth conditions, it shows a preference for substituting on Se sites. Interestingly, only SbIn defects do not form impurity states in the band gap. Additionally, SbIn, SbS, and SbSe show a reduction in the band gap. Our results reveal that Sb-doped CISSe exhibits enhanced optical absorption in the IR to visible regions, leading to increased photocurrent generation and improved photovoltaic device efficiency, consistent with our experimental findings. These findings provide valuable theoretical insights into the influence of Sb-doping in CISSe, aiding the design of effective metal chalcogenide PV.