Properties of oxygenated cadmium sulfide (CdS:O) and their impact on CdTe device performance

In this work, we report on the development of a reactive sputtering process for CdS:O for high efficiency CdTe solar cells. X-ray diffraction, UV-Vis-NIR spectrophotometry, and Rutherford backscattering spectrometry were used to characterize the crystal structure, composition, and optical properties, respectively. All films were slightly Cd-rich, while the bulk oxygen content increased up to 45 at. % in direct proportion to the O₂ partial pressure. Optical absorption in cells was reduced by increasing the oxygen fraction in the sputtering ambient. Optimal performance was obtained from cells with CdS sputtered in a 6% O₂/Ar ambient, yielding efficiency >14% and V_OC >840 mV.