CdTe and ZnTe Polycrystalline Thin Films for Photovoltaic Applications

Polycrystalline CdS/CdTe thin film solar cells are the leading candidate for low-cost, large-scale terrestrial photovoltaic applications. This work describes some aspects of CdTe and ZnTe polycrystalline thin films prepared by pulsed laser deposition (PLD) technique for photovoltaic applications. In most cases, CdTe cells are subjected to a post-growth heat treatment, which involves annealing in the presence of CdCl2. This treatment usually results in grain growth, improves device characteristics like open circuit voltage (Voc) and fill factor (FF). Here a novel CdCl2 treatment for CdS/CdTe thin film solar cells and their structural and optoelectronic characteristics have been discussed. CdTe films were deposited onto chemical bath deposited CdS films. The composite films were subjected to rapid thermal annealing (RTA) to observe simultaneous grain growth in both CdS and CdTe layers. Unwashed CdS layer containing residual CdCl2 for initiating grain growth in CdTe layer was utilized. Thus, successful elimination of an additional step of CdCl2 treatment after CdTe deposition in CdTe solar cell was established.