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-treat...