Reduced potential fluctuation in a surface sulfurized Cu(InGa)Se2

Cu(InGa)Se2 (CIGSe) that was grown under Cu-deficient conditions exhibited potential fluctuations in its band structure. When the donor and acceptor density is high and compensated for in CIGSe, the local deviations in the spatial distribution of donors and acceptors result in potential fluctuations. This study demonstrates the reduced potential fluctuation of CIGSe using the surface sulfurization process. We performed photoluminescence (PL) analysis on non-sulfurized and sulfurized CIGSe in the temperature range 15–100 K with varying excitation laser power values (1.7–180.6 mW/cm2). The results state that sulfurized CIGSe exhibited reduced potential fluctuations in comparison with non-sulfurized CIGSe. The depth of potential wells in sulfurized CIGSe was 5 meV, which was significantly reduced compared to that of non-sulfurized CIGSe (13 meV). This implies that surface sulfurization led to the substitution or reduction of donors (VSe 2− and/or InCu 2+) due to reaction with S. Subsequently, the compensation was moderated in sulfurized CIGSe.

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