Effect of proton irradiation energy on high resistivity silicon heterojunction solar cells

Silicon solar cells are used anew on satellites for low-earth-orbit missions to comply with New Space demand. Studies are thus emerging to evaluate the resilience of modern silicon solar cells technologies towards space environment. In this study, we chose to irradiate 160 µm-thick silicon heterojunction solar cells to 1 & 3 MeV protons. 1 MeV and 3 MeV protons have a stopping range in Si of 16 µm and 92 µm, respectively. These proton irradiations lead to strong carrier removal effect along with carrier lifetime degradation. This study aims to investigate their effects on high resistivity Ga doped (60 Ω.cm) silicon bulk. Highly degraded IV performances are observed at fluences of 1012 cm-2 and beyond, with 3 MeV proton irradiations leading to more dramatic damages. A modeling study confirms the strong majority carrier concentration decrease with local in-plane areas even showing a conductivity type inversion for 1 MeV protons at a fluence of 1012 cm-2. Finally, we highlight the importance of using a bias light for spectral response measurements, as it was required to match the JSC obtained from IV and external quantum efficiency measurements. It thus suggests a high light injection dependence for the recombination activity of the proton irradiation-induced defects.