Efficient Cd(Se,Te) Solar Cells with Cd(O,S,Se,Te) at the Front Interface

Cadmium sulfur selenide (Cd(S, Se)) at the front interface has been demonstrated to be a deleterious photo-inactive region in Cd(Se, Te) solar cells, which typically results in low open circuit voltages (VOCs) and short circuit current densities (JSCs). Thus, it is crucial to avoid the formation of Cd(S, Se) alloy to improve the device performance. In this work, we found that oxygen management during the device fabrication is a facile strategy to manipulate the atomic interdiffusion and avoid the Cd(S, Se) formation at the front interface. The key is to deposit both the CdS and CdSe layers and conduct the post CdCl2 treatment with oxygen incorporation, while oxygen should be absent during the CdTe deposition to avoid over-oxidization due to the high deposition temperature. Through oxygen management, CdS/CdSe/CdTe solar cells with efficiencies over 19% are demonstrated, which is among the champion CdTe solar cells.