Enhancing CdS/CdTe thin-film solar cell efficiency: The role of oxygenation in close-spaced sublimated CdS layers

Polycrystalline CdTe photovoltaics are promising alternatives to silicon-based solar cells, with device performance strongly influenced by the n-type CdS window layer. Close-spaced sublimation (CSS) efficiently deposits CdS layers, enabling full device fabrication. In this study, we present a comprehensive investigation into the impact of oxygenation over a wide range of concentrations (0% - 30%) on close-spaced sublimated CdS (CSS-CdS:O) films - an aspect which has not been reported previously. The close-spaced sublimated CdTe (CSS-CdTe) was used as the photon-absorbing layer. Furthermore, it examines the consequent effects on CSS-CdS:O/CSS-CdTe solar cell parameters. Material properties were characterized by means of UV–visible spectroscopy (UV–Vis), Field Emission Scanning Electron Microscope (FE-SEM), and X-ray Photoelectron Spectroscopy (XPS), while a solar simulator was utilized for device characterization. The optimized CdS:O layer with 20% oxygen incorporation yielded the best power conversion efficiency of 9.2%, representing around a 70% increment compared to the oxygen-free sample. The CdS/CdTe device exhibited an open-circuit voltage ( V OC ) of 0.678 V, short circuit current ( J SC ) of 24.8 mA cm - ², and fill factor ( FF ) of 55% under the AM 1.5 G illumination.