Characterization of Degradation and Damage Coefficient of Ga‐Doped PERC Space Solar Cells Under 1 MeV Electron Irradiation

ABSTRACT The degradation of passivated emitter and rear cell (PERC) fabricated on Ga‐doped p‐type substrates under varying levels of electron irradiation is analyzed for applications on satellites in Low‐Earth Orbit (LEO). While the optical properties, as characterized by the reflectance spectra, remain unchanged up to a 1 MeV electron fluence of 1 × 10 14 cm −2 , significant degradation is observed in the electrical properties of the solar cells. A dramatic decrease in internal quantum efficiency, particularly in the medium and long wavelength regions, indicates an increase in bulk recombination as the electron fluence increases. At the highest electron fluence (1 × 10 14 cm −2 ), the AM0 efficiency drops from 19.32% to 14.91%, corresponding to a relative loss of 22.8%, primarily due to reductions in open‐circuit voltage and short‐circuit current. The electrical irradiation damage coefficients (K L ), used to quantify degradation in the minority carrier diffusion length, are calculated in the range of (3.8–7.5) × 10 −11 electron −1 before a 200°C annealing, with small variations attributed to sample structure and experimental scatter across different fluences. Partial recovery of degraded solar cells under dark annealing is also demonstrated. These findings provide valuable insights into the degradation of Ga‐doped PERC solar cells under electron irradiation and serve as a reference for the design of solar arrays used in LEO spacecraft. Assuming that the degradation coefficient of Ga‐doped silicon follows a similar dependence on doping concentration as B‐doped silicon, simulations were performed to optimize the bulk resistivity and solar cell thickness for LEO applications and 1 MeV electron irradiation up to 1 × 10 14 cm −2 . The results of these simulations suggest that an optimum thickness of approximately 40–70 μm is preferable for low‐resistivity substrates, but an interesting alternative is to use high‐resistivity substrates (around 200 Ω.cm), which reduces irradiation‐induced damage and enables thicker wafer designs with improved EOL efficiency.