Experimental Study of the Degradation of Silicon Photovoltaic Devices under Ultraviolet Radiation Exposure

Abstract

This paper presents an analysis of the effects of ultraviolet (UV) exposure on amorphous silicon (a-Si), bare crystalline silicon (c-Si), and epoxy resin encapsulated c-Si devices. The long-term reliability of photovoltaic (PV) modules is crucial in ensuring the viability of PV as a successful source of energy. Accelerated UV ageing methods are required to quickly evaluate the UV durability of module materials. A UV exposure unit was designed and constructed and provided an average of 45.7 W/m 2 of UV irradiance over the exposure area with a nonuniformity of 14.9%. The a-Si devices lost up to 44% of maximum power ( P m a x ) at Standard Test Conditions over 500 hours of exposure to UV, with maximum losses of 11% in short-circuit current ( I s c ), 11% in open-circuit voltage ( V o c ), 23% in voltage at P m a x ( V m p p ), and 29% in current at P m a x ( I m p p ). The epoxy resin encapsulated samples lost up to 6.4% in P m a x , 6% in I s c , and 7% in I m p p with the changes in V o c and V m p p being random. The bare cells showed relatively little degradation. UV radiation thus accelerates the degradation of a-Si devices, deteriorates polymeric encapsulates of modules, and possibly affects the antireflective coatings applied on solar cells.