Silicon's cosmic comeback: Temperature-dependent performance and radiation stability of ultra-thin silicon heterojunction solar cells for space applications

Growing demand for cost-effective satellites has renewed interest in silicon (Si) cells for space missions. However, these cells experience significant radiation-induced performance loss, which can be mitigated using ultra-thin wafers. Recently, ultra-thin Si heterojunction (SHJ) cells have emerged as strong candidates for low-cost, lightweight satellites. Their behaviour under space-relevant temperatures and air mass zero conditions, before and after electron irradiation, is therefore essential to understand. This study examines the temperature-dependent performance of ultra-thin (50 μm) SHJ cells under such conditions and compares their behaviour to 180-μm SHJ cells and cell structures without heterojunctions. We find that the performance of SHJ cells drops sharply at low temperatures regardless of wafer thickness, dominated by reduced fill factor, whereas structures without heterojunctions show linear improvement as temperature decreases. Notably, irradiated ultra-thin SHJ cells show a self-curing capability after annealing at 80 °C, enabling partial performance recovery even during electron irradiation in space. Additionally, their specific power surpasses that of the other structures across −20 °C to 80 °C. The established models reproduce the experimental trends, offering deeper insight into their low-temperature behaviour. These findings reveal a low-temperature performance threshold for SHJ cells and underscore their importance for evaluating and optimising them in space applications. • Ultra-thin SHJ cells offer high specific power and radiation tolerance, ideal for lightweight, low-cost space use. • Ultra-thin SHJ cells self-heal after 80 °C annealing, partly restoring performance during electron irradiation. • Heterojunction interfaces cause strong low-temperature sensitivity due to band offsets and doped layer properties. • Though fill factor drops at low temperatures, ultra-thin SHJ cells still outperform thicker and homojunction designs in power-to-weight ratio. • Models accurately match experiments, guiding SHJ cell design under AM0 spectrum and extreme temperatures.