Leakage current and performance loss of thin film solar modules

Abstract

Due to the system voltage, solar modules in power plants have to withstand continuous high bias voltages between the absorber/conductive layers of the solar module and the grounded mounting structure. Mon et al.^{1, 2} showed in several publications during the 1980s that the charge transferred by this electrical field is leading to strong electrochemical degradation effects in the modules, both crystalline and thin-film. The bias voltage, especially for thin film modules, can cause transparent conductive oxide (TCO) corrosion via sodium diffusion through the glass together with the presence of water molecules in the TCO/glass interface.^{3, 4} Based on these previous works, we analyzed the accelerated degradation effects as well as the end of life conditions of different module technologies and module designs. By means of indoor climate chamber and outdoor experiments and based on a simple model we give an example of service life time in terms of electrochemical damage due to high bias voltages caused by the PV system voltage.