Degradation mechanisms of Cu(In, Ga)Se{sub}2-based thin film PV modules

摘要

Long-term stability is a fundamental requirement in order for CIGS thin film solar cells to become an industrial success. From accelerated lifetime tests of CIGS devices in damp heat conditions, we observe that modules show less good long-term stability than cells. In particular, increasing series resistance during damp heat exposure is seen to have a strong impact on the fill factor. We show that this phenomenon is related to the additional functional parts that are introduced as cells are monolithically integrated into modules. In order to explain the observed degradation, we evaluate the influence of each zone of the interconnect separately. We specifically address the issues of front contact degradation, shunting between cells, ohmic losses in the interconnect via, and corrosion of the back contact. Degradation of the interconnect via is found to be a major cause of performance loss.