Wet chemical etched CdTe thin film solar cells

Wet chemical etching process on as-deposited CdTe surface using nitric-phosphoric (NP) acid improved the efficiency of CdS/CdTe solar cells from 10.1% to 13.8%. Nitric-phosphoric (NP) acid solution etched native oxide (TeO2) layer and resolved excess cadmium on CdTe surface. After the heat treatment process activated the CdCl2, CdO layer which was believed to be a diffusion barrier of chlorine did not grow on the etched CdTe surface and new (VCd2−–2ClTe1+)0 complexes was located at EV + 0.045 eV. New (VCd2−–2ClTe1+)0 complexes acted as a shallow acceptors and induced to improve Voc and Jsc. The surface of CdTe thin film has been studied using Scanning Electron Microscope (SEM), X-ray Diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and low temperature Photoluminescence (PL).

► CdO layer on the CdTe thin was believed to be a diffusion barrier of chlorine. ► Excess Cadmium on the surface of CdTe thin film was the origin of CdO layer. ► Wet chemical etching process removed the excess Cadmium on CdTe surface. ► New (VCd2−–2ClTe1+)0 complexes existed at the wet chemical etched CdTe thin film. ► (VCd2−–2ClTe1+)0 acted as a shallow acceptors and induced to improve Voc and Jsc.