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 VOC >840 mV.