Reliability investigation on CdTe solar cells submitted to short-term thermal stress

In this paper, we investigate the effect of short-term thermal stresses in CdTe thin film solar cells.The CdTe solar cells under test are manufactured with physical vapour deposition on soda lime glass in superstrate configuration. Different characterization techniques were used to study the reliability of the solar cells. In particular, external quantum efficiency (EQE) and electroluminescence (EL) measurement were applied in order to investigate the physical processes responsible for degradation. Through this analysis, we give a broad overview of degradation effects using both electrical and optical measurement and correlating the results. We show that (i) during short-term thermal stresses a soft degradation occurs, (ii) the series resistance of the cells increases and (iii) degradation is preliminarily ascribed to the generation of crystal defects due to the diffusion of copper or oxygen atoms in the CdTe solar cells.