Remarkable Recovery of Proton-Irradiated Cu(In,Ga)Se₂‑Based Solar Cells for Space Applications: Thermaland Light Annealing Treatment

In this work, we present an experimental study of Cu(In,Ga)Se₂ (CIGS) thin film solar cells (SC) irradiated with protons with energy values in the range of 80 to 180 keV, under a total fluence of 3.45 × 10¹⁴ protons/cm², simulating the space’s harsh environment. The irradiation process is intended to create a broad distribution of defects across the CIGS/CdS interface and the top region of the CIGS layer, resulting in the formation of defects throughout the depletion region. Due to the irradiation, a drastic reduction of 92% in the power conversion efficiency was obtained. Notably, the SCs kept working. The luminescence suffered a broadening, red-shift, and decrease in the signal-to-noise ratio. The almost total recovery of both efficiency and luminescence was obtained through several thermal annealing steps with increasing temperature intercalated with light-soaking (LS) treatments at room temperature, whereas keeping the irradiated SCs at room temperature in the dark and ambient atmosphere did not allow a significant recovery. The power conversion efficiency remarkably recovered to 84% of the pre-irradiation value after all the recovery treatments. The results demonstrated that the thermal annealing steps are of greater relative importance compared with the LS treatments. Evidence was found for the involvement of the <i>V</i>_Cu and the <i>V</i>_Se-<i>V</i>_Cu complex on the dominant radiative recombination channels. This study demonstrates the self-healing behavior of CIGS and the adaptability of CIGS to induced damage, allowing charge carrier transport channels to be re-established after recovery. Additionally, this work reaffirms the potential of the CIGS technology in the actual context of space exploration, when satellites need to be smaller in size and durable to mitigate space debris generation.