A study of back contacts of CdTe thin film solar cells

Abstract

We have prepared polycrystalline CdTe thin films by close-spaced sublimation，then the film surface was been etched by nitric-phosphoric acid. After etching，the grain boundaries of CdTe thin films are broadened and it could be seen clearly that the surface became polished and more smooth, when observed by scanning electron microscope (SEM). After NP etching，highly conductive Te-rich layer is formed on the surface of CdTe thin film，as detected by X-ray diffraction (XRD). Four types of back-contact layers, including Cu, Cu/ZnTe：Cu, ZnTe：Cu and ZnTe/ZnTe：Cu were deposited respectively on the etched CdTe thin film，and the influences on the solar cells performance were compared. Our studies showed that the performance of CdTe solar cells with ZnTe/ZnTe：Cu complex back-contact layer was better than those with other back-contact layers，and the highest conversion efficiency of 13.38% has been obtained for CdTe polycrystalline thin film solar cells of 0.5cm2 size.