Abstract
The effects of post-deposition processes such as 
dip and/or annealing in air on the material and device properties of vacuum-evaporated Au-CdTe/CdS-TO heterojunction solar cells have been investigated. The 
dip followed by air annealing at 
for 5 min improved the device efficiency significantly, resulting in decreased CdTe resistivity and enhanced grain size. The temperature-dependent current - voltage analysis indicated that above 280 K interface recombination dominates the current transport mechanism for the as-grown samples, while depletion region recombination starts to be dominant after annealing the samples with . Below 280 K multistep tunnelling is identified to be the dominant transport mechanism. Frequency-dependent capacitance - voltage studies revealed that after annealing with the density of interface states decreases and the quality of the heterointerface improves. The capacitance of the CdS/CdTe heterojunctions has been analysed using a model based on the existence of a single dominant trap level, identified at 0.40 eV above the valence band with a concentration of 
.
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