Photoluminescence Investigations of CdSeTe Absorbers to Determine How Selenium Concentration Influences Attainable Voltages

CdTe photovoltaics has enjoyed considerable performance improvements in the last several years due in large part to the incorporation of the CdSeTe alloy within the absorber layer. However, cell and module open-circuit voltage improvements are not nearly as large as some metrics suggest they should be. It has recently been shown by others that, in addition to substantially increased photoluminescence quantum yield - which would be expected to increase voltage - high selenium incorporation creates significant band tail states, which would be expected to decrease voltage. Using photoluminescence spectroscopy, this work aims to quantify this relationship as a function of selenium concentration, and potentially identify an optimal concentration which maximizes implied voltage. Also shown are multiple-microsecond lifetimes in CdTe-based polycrystalline absorber films deposited directly on the front contact with no passivating layers at either interface, an uncommon result in presently available literature.