Stress behaviour of CuInS2 thin film PV modules studied by a specific test structure

Abstract

CuInS2 CIS thin film photovoltaic devices have been exposed to damp heat stress 85 relative humidity at 85 C in order to test long term stability. Degradation of the series resistance Rs has been found the major reason for module degradation. Specially designed transmission line test structures were used to get access to the ZnO sheet resistance Rsq and the Mo ZnO contact resistance Rc, the most important contributions to Rs. The degradation of Rc is strongly dependent on the point of time when P2 is made. Additionally solar cells were exposed to the same damp heat stress. These cells have no metal grid and their front contact is achieved by contacting the ZnO to a molybdenum pad in the same way as it is found for the single cells of modules. After 540 hours of unprotected exposure to damp heat these solar cells still show about half of their initial efficienc