The study on saturation current and ideality factor of CdTe solar cell based on CdS window layer deposited with hydrogen peroxide

Abstract

By adding hydrogen peroxide (H2O2) to the solution, a more compact cadmium sulfide (CdS) film with larger optical band gap is fabricated by chemical bath deposition method. The oxidation of CdS is confirmed by the formation of cadmium sulfate (CdSO4) in the CdS window layer via x-ray photoelectron spectroscopy investigation. The analysis of quantum efficiency considering the alloy CdS1−yTey shows that the oxygenated CdS suppress the S-Te interdiffusion, which promotes the spectral response in short-wave range. Moreover, this oxygenated CdS layer promoted the conversion efficiency of the cadmium telluride (CdTe) based solar cell from11.2% to 14.0% due to the improvement of open-circuit voltage and the fill factor. The transport mechanisms of saturation current are evaluated by temperature dependent current–voltage curves. Results show that the oxygenated window layer reduces both the interfacial and bulk recombination, thus improves the ideality factor. The decrease of bulk recombination in depletion region is attributed to the fewer trap level induced from S-Te interdiffusion. The decrease of interfacial recombination is attributed to the larger optical band gap of oxygenated CdS, which results in a spike-like conduction band alignment at CdS/CdTe heterojunction.