Electron irradiation effects on ultra-thin silicon IBC solar cells of varying thickness: Analytical modelling and experimental demonstration of the critical design factors of silicon solar cells for space application

In the “Space 2.0” era, space missions demand solar technologies that are lightweight, efficient, and cost-effective. Silicon (Si) solar cells offer a mature, low-cost solution, with back-contact (BC) architectures achieving the highest conversion efficiency among Si-based designs. However, typical terrestrial Si cells with thicknesses of 130–150 µm face limitations in radiation tolerance and mass, both critical for space applications. While thinner designs have demonstrated improved resilience, most studies remain qualitative and lack a quantitative framework—particularly for BC cells, for which the irradiation response remains largely unexplored. To address these gaps, this work investigates ultra-thin Si back-contacted (UTSBC) solar cells as a model system to establish a unified physical framework that quantifies the interplay between absorber thickness, junction location, carrier diffusion length, and surface recombination under electron irradiation. We further introduce the concept of a “critical thickness”—a threshold below which radiation-induced performance degradation is significantly suppressed—thereby linking microscopic degradation mechanisms to device-level design rules for radiation-hardened Si photovoltaics in future space applications.