Radiation-induced degradation of GaAs and InGaP solar cells in space environments: a predictive model

Solar cells in space are exposed to a harsh radiation environment, where high-energy electrons, protons, and ions can significantly degrade their performance over time. Quantifying the impact of various radiation sources is crucial for predicting solar cell degradation throughout the life of a space mission. This study presents a first-principles method for calculating electron radiation-induced damage in GaAs and InGaP solar cells using a defect-assisted recombination model. Leveraging Shockley-Read-Hall theory, the model quantifies the minority carrier diffusion length damage coefficient (KL)-the most important factor for current collection efficiency-under high-energy electron irradiation. KL is integrated into the drift-diffusion model for solar cell operation. The results show a strong correlation between radiation energy, defect formation, and the degradation of key solar cell parameters such as short-circuit current (Isc) and maximum power (Pmax). The model highlights the superior radiation resistance of p-type over n-type materials and demonstrates the greater resilience of InGaP compared to GaAs under electron radiation. These findings are validated against existing data and provide a predictive framework for assessing solar cell performance in space environments. We conclude that although InGaP typically serves as the current-limiting layer in modern multijunction solar cells (MJSCs), GaAs is more vulnerable to radiation damage. At higher radiation fluence levels, GaAs can surpass InGaP in degradation, becoming the current-limiting layer after crossing a critical "knee point. " The large rate of degradation of GaAs can cause a runaway effect leading to sudden fall in solar power generation. To meet the power demands of long-term space missions, such as those aboard space stations or interplanetary voyages, preventive measures-such as optimizing junction depth, employing ultra-thin MJSC stacks, and incorporating light management substructures-are recommended to slow GaAs degradation and extend the operational life of solar cells. (author)