The effect of MoOx inter-layer on thin film CdTe/CdS solar cell

Back contact improvement is one of the most crucial issues for the formation of a low resistance contact and enhanced efficiency in CdS/CdTe based photovoltaic cells. We studied Ni/CdTe back contact formation with x-ray photoelectron spectroscopy (XPS) and ultraviolet photoelectron spectroscopy (UPS), and observed the effect of a thin MoOx inter-layer between Ni and CdTe films. Contrasting differences in the interface formation and core level structure were observed, indicating that the presence of a thin MoOx inter-layer was effective in reducing the reaction between Ni and the native tellurium oxide at the CdTe surface. The improvement of device performance is explained based on the evolution of core levels and the valence band region during the Ni/MoOx/CdTe interface formation, wherein MoOx serves as a high work function buffer layer.