Radiation-shielding glass with tailored Al-doped zinc oxide (AZO) coatings for durable space photovoltaic modules

In space applications, photovoltaic cells, which are used to provide power and enable the self-operation of satellites, are exposed to various extreme stressors. Among these, electron radiation induces various defects in photovoltaic cells, thereby accelerating performance degradation. To mitigate radiation-induced damage, effective shielding methods must be integrated into the photovoltaic module. In this study, we investigated aluminum-doped zinc oxide (AZO) thin-film-coated quartz glass as a potential radiation-shielding cover glass for III-V multi-junction space photovoltaic cells. To enhance the shielding performance, two post-treatment methods, ultraviolet (UV) treatment and thermal annealing, were tested. It was observed that thermal annealing improved the crystallinity of the AZO film and enhanced its effective shielding against electron radiation. Under electron irradiation at 1.2 MeV with a fluence of 1 × 10¹⁵ to 3 × 10¹⁵ e^- cm^-2, the thermally annealed AZO-coated glass demonstrated superior radiation-shielding performance compared to bare quartz glass. Consequently, when applied to our in-house-developed space photovoltaic modules incorporating a 4G32C III-V photovoltaic cell, they resulted in an improvement in efficiency degradation, from 4.18% to 2.37%, after electron irradiation at 1.2 MeV and 1 × 10¹⁵ e^- cm^-2. These findings demonstrate that AZO thin films, when prepared with appropriate post-treatment, can serve as reliable radiation-shielding layers, offering significant potential enhancement to the long-term durability and operating stability of space photovoltaic modules.