Observation of self-healing and blue response enhancement in c-Si solar cells exposed to electron irradiation

Abstract

The effects of electron irradiation on the performance of mono-crystalline silicon (c-Si) solar cells were investigated by examining various electron doses, ranging from 225 to 900 Gy, with an energy of 8 MeV. The study focused on dose-dependent degradation in cell behavior resulting from irradiation. Detailed analysis was conducted through dark and illuminated current-voltage (I-V) measurements, external quantum efficiency (EQE) measurements, capacitance-voltage (C-V) measurements, and conductance-voltage (G/omega-V) measurements. The observed degradations were thoroughly analyzed, quantified, and discussed by comparing the results obtained from complementary electrical and optical characterizations of the cells before and after irradiation. The experimental findings indicated that the degradation in cell parameters was attributed to irradiation-induced defect formations in the base layer. However, the devices were found to be resilient to defect formations in the emitter and near the depletion edge of the base. After 52 months of irradiation, significant self-healing effects and improvements in blue response were observed in the cells, likely due to additional positive charge formation in the nitride layer from oxynitride formation in the ambient atmosphere over time, accelerated by radiation damage. This was confirmed by both illuminated I-V and EQE measurements.