Radiation degradation mechanisms of GaInP/GaAs heterojunction solar cells following proton, electron and sequential irradiation

This study focused on the damage disparity and coupling effects of 2 MeV protons and 1 MeV electrons in irradiated GaInP/GaAs HJT solar cells. It was found that the V_oc , J_sc and EQE curve exhibited similar degradation levels at proton and electron fluences of 5 × 10¹¹ cm⁻² and 8 × 10¹⁴ cm⁻², respectively. An equivalency factor of R_ep = 1.55 was determined for the GaInP/GaAs HJT cell, resulting from the far greater displacement damage effectiveness of 2 MeV protons compared to 1 MeV electrons. DIV analysis showed that both J_diff and J_rec increased linearly with fluence, with J_rec being the dominant component. Defect analysis revealed that 2 MeV protons uniquely introduced the H₂ (E_v + 0.32 eV) defect. Despite these differences in specific defects, their overall impact on the SRH recombination lifetime was similar when compared at an equivalent displacement damage dose. Sequential irradiation experiments confirmed that the coupled damage did not introduce new defects but resulted in a linear superposition of the defects induced by individual irradiations, indicating no significant synergistic effect.