Postdeposition Sulfurization of CuInSe ₂ Solar Absorbers by Employing Sacrificial CuInS ₂ Precursor Layers

Herein, a new route of sulfur grading in CuInSe2 (CISe) thin-film solar absorbers by introducing an ultrathin (<50 nm) sacrificial sputtered CuInS2 (CIS) layer on top the CISe. Different CIS compositions (Cu-poor to Cu-rich) are analyzed, before and after high-temperature treatment selenium (Se)- or selenium+sulfur (SeS)-rich atmospheres. An [S]/([S] + [Se]) from surface into bulk Se- SeS-treated samples is observed, evidence formation mixed CuIn(S,Se)2 phase Raman analysis X-ray diffraction provided. The optical bandgap quantum efficiency measurements cells increased 1.00 eV for CISe reference 1.14 1.30 bilayer samples, respectively. A ≈150 mV higher VOC observed sample, but cell exhibits blocking characteristics resulting lower as compared with reference. This attributed internal electron barrier at interface sulfur-rich layer. difference reaction routes possible ways improve developed sulfurization process discussed.