CdTe polycrystalline thin film solar cells have a strong potential in scalability. They have shown long-term stable performance and high efficiency up to 16.5% under AM1.5 illumination. Amongst several attractive features high chemical stability of CdTe and a simple compound formation are the most important ones for large area production of solar modules. A further simplification has been done by substituting the CdCl2 step by treating CdTe films in an atmosphere containing a non toxic gas that is inert at room temperature, like HCFCl2, that belongs to the Freon© family. The treatment is typically done at a temperature of 400°C, for a few minutes and in an atmosphere of 100 mbar of Ar containing 15% of HCFCl2. The change in the morphology of CdTe films after treatment is very similar to that obtained with CdCl2 treatment and an increase in the size of small grains is always observed. This process has been applied by N. Romeo et al. CdTe thin films deposited by on close spaced sublimation (CSS) with very interesting results (15.8% efficiency). In this work the application of this novel “activation process” on physical vapor deposited cells will be described and a comparison of physical and electrical features with the standard process and with CSS deposited layers will be presented.
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