Dependence of carrier lifetime on Cu-contacting temperature and ZnTe:Cu thickness in CdS/CdTe thin film solar cells

Cu diffusion from a ZnTe:Cu contact interface can increase the net acceptor concentration in the CdTe layer of a CdS/CdTe photovoltaic solar cell. This reduces the space-charge width (W-d) of the junction and enhances cur-rent collection and open-circuit voltage. Here we study the effect of Cu concentration in the CdTe layer on carrier lifetime (tau) using time-resolved photoluminescence measurements of ZnTe:Cu/Ti-contacted CdTe devices. Measurements show that if the ZnTe:Cu layer thickness remains constant and contact temperature is varied, tau increases significantly above its as-deposited value when the contacting temperature is in a range that has been shown to yield high-performance devices (-280 degrees to -320 degrees C). However, when the contacting temperature is maintained near an optimum value and the ZnTe:Cu thickness is varied, tau decreases with ZnTe:Cu thickness. Published by Elsevier B.V.