Comparative Study of Back Surface Fields on the Radiation Tolerance of GaInP Solar Cells Under 1 MeV Electron Irradiation

Back surface field (BSF) materials are key functional layers that suppress rear-surface recombination and regulate carrier transport in III–V solar cells. This work investigates the performance degradation behavior of GaInP solar cells with AlInP and AlGaInP BSF layers under 1 MeV electron irradiation. Through a combination of optoelectronic measurements and TCAD simulations, the carrier transport and recombination mechanisms before and after irradiation are comprehensively analyzed. Although both devices deliver comparable initial photovoltaic performance, distinct degradation trends emerge under high-fluence electron irradiation. After a cumulative fluence of 1 × 1015 e/cm2, the cell with an AlInP BSF suffers more severe degradation owing to inferior radiation hardness. Irradiation-induced defects reduce the minority-carrier lifetime and enhance Shockley–Read–Hall (SRH) nonradiative recombination, resulting in a 14% drop in short-circuit current density. In contrast, the AlGaInP BSF exhibits favorable radiation tolerance, and the corresponding device undergoes only a 2% loss in short-circuit current density. The influence of the BSF structure on carrier transport and recombination is systematically analyzed, providing experimental and theoretical support for the design of space-grade GaInP top cells.