Study of defects in polycrystalline CdTe using DLTS

The defect distribution of polycrystalline Cadmium Telluride (CdTe) deposited by Close Spaced Sublimation (CSS) is investigated using Deep Level Transient Spectroscopy (DLTS). CdTe solar cells were fabricated with different post deposition processing, such as CdCl2 heat treatment (HT) and Cu doping. The devices were characterized by standard Current-Voltage (JV) and Capacitance-Voltage (CV) measurements. DLTS measurements identified peaks corresponding to minority carrier electron traps with an activation energy between 0.26 eV to 0.48 eV The intensity and position of the peaks were found to be dependent on CdCl2 HT and the level of Cu doping. A number of majority and minority carrier traps were observed in cells processed with higher than optimal Cu concentration. The presence of deep defects in untreated and Cu doped samples were indicative of low minority carrier lifetime on those cases.