Rapid Healing: How hydrogenation supercharges recovery of electron-irradiation defects in Ga-doped PERC solar cells

Due to significantly lower costs than compound semiconductor counterparts, there is increasing interest in using silicon solar cells for cost-sensitive space missions, particularly in low Earth orbit (LEO). A major concern is, however, that the minority carrier lifetime (lifetime) of silicon solar cells degrades severely under high-energy electron irradiation. Fortunately, thermal and hydrogenation processes can potentially recover all the irradiation losses. This work studies these defects and their recovery using contactless lifetime measurement and deep-level transient spectroscopy (DLTS). Both fired and unfired Ga-doped passivated emitter and rear contact (PERC) solar cell precursors are used in this work. The precursors were irradiated with 1 MeV electrons and annealed at 300 °C and 380 °C, respectively. All the samples exhibited lifetime recovery, with fired samples recovering faster and achieving higher saturated lifetime. After ∼360s of annealing at 380 °C, the irradiated fired samples recovered to their pre-irradiation lifetime, whereas the irradiated non-fired samples required 71.5 times longer (25,740 s). Remarkably, longer annealing caused reductions in lifetime, likely due to surface-related degradation. The DLTS measurements revealed a clear reduction of recombination-active defects after annealing, including V-V + and C i -C s in irradiated fired samples and V-V + in irradiated unfired samples. This study demonstrates that the firing process is critical for optimizing the recovery of irradiation damage in silicon solar cells. Hydrogenation of the silicon bulk results in quicker recovery and superior End-of-life performance compared to thermal recovery without hydrogen. Therefore, Ga PERC with bulk hydrogenation can recover radiation-induced damage, rendering it suitable for LEO missions. • Irradiation damage and recovery of commercial PERC precursors were quantitatively evaluated. • The V-V + and C i -C S defects in Si PERC substrate after 1 MeV electron irradiation were characterised by DLTS. • Full recovery from irradiation damage was confirmed in hydrogenated samples, unlike that in non-hydrogenated samples. • Hydrogenated samples exhibited 71.5 times faster recovery than non-hydrogenated samples. • Superior recovery in hydrogenated samples was driven by quicker bulk hydrogen movement than silicon self-interstitials.