Band offsets engineering at CdxZn1-xS/Cu2ZnSnS4 heterointerface

CdxZn1-xS/Cu2ZnSnS4(CZTS)-based thin film solar cells usually use Cd S as a buffer layer, but due to its smaller band gap(2.4 e V), Cd S film has been replaced with higher band gap materials. The cadmium zinc sulfide(Cd Zn S) ternary compound has a higher band gap than other compounds, which leads to a decrease in window absorption loss. In this paper, the band offsets at CdxZn1-xS/Cu2ZnSnS4(CZTS) heterointerface are calculated by the first-principles, densityfunctional and pseudopotential method. The band offsets at Cd1-xZnxS/CZTS heterointerface are tuned by controlling the composition of Zn in Cd1-xZnxS alloy, the calculated valence band offsets are small, which is consistent with the commonanion rule. The favorable heterointerface of type-I with a moderate barrier height(< 0.3 e V) can be obtained by controlling the composition of Zn in Cd1-xZnxS alloy between 0.25 and 0.375.