Developing Transition Metal Oxide-Based Electron-Selective Contacts for High-Performance, Non-Epitaxial InP Solar Cells

Despite superior radiation tolerance and high specific power, high costs associated with traditional epitaxial growth methods hinder the adoption of III-V solar cells for price-sensitive space applications. By utilizing industry-scalable sputtering techniques, we demonstrate a non-epitaxial, heterojunction InP solar cell utilizing ZnO as an electron-selective contact (ESC), achieving an AM0 efficiency of 7.27%. This work shows an absolute efficiency improvement of 1.25% from previous comparable devices. We attribute the improvement to efficient carrier extraction and reduced surface recombination from the changes in sputtering technique, nanocrystalline nature of ZnO, and highly doped In2O3:SnO2 (ITO). Given the well-characterized, superior radiation resilience of InP, this work positions InP as a cost-effective, long-lifespan alternative to GaAs and Si for radiation environments. Furthermore, we estimate a potential savings of ~86% in growth costs by removing the need for epitaxy. Preliminary results highlight pathways for further performance enhancements, including multilayer ESC schemes and optimized plasma treatments, with an AM0 efficiency of 10.79% and peak metrics of Jsc of 27.6 mA/cm2, Voc of 702 mV, and FF of 76.1%. This cost-effective approach warrants further study for high-efficiency InP-based technologies tailored for low-cost space applications. Future work will focus on optimizing device interfaces and evaluating radiation resilience.