Effect of post-deposition annealing time on photovoltaic performance of wide bandgap trigonal selenium solar cells

Selenium (Se), due to its inherent stability, low environmental toxicity, and adaptability to emerging applications such as indoor light harvesting and tandem solar cell architectures, has re-emerged as a promising material for next-generation photovoltaic power generation. However, the actual efficiency of selenium-based devices remains far lower than theoretical predictions, mainly due to the challenges in balancing the control of crystallinity and the mitigation of defects during the thin film manufacturing process. In this study, the role of the annealing time in optimizing the microstructure and electronic properties of selenium thin films was systematically investigated. By optimizing the annealing conditions to balance crystallization and material stability, we achieved an efficiency of 6.08 % while maintaining long-term operational durability. The contradiction between thin film microstructure and photovoltaic performance induced by annealing time essentially reflects a competition between thermodynamic driving forces and kinetic limitations over time. Advanced characterization techniques show that extended defects rather than point defects dominate the recombination losses, providing crucial insights into the efficiency limitations. This work establishes a scalable processing framework that links fundamental understanding with industrial compatibility, offers a pathway to unleash the full potential of selenium in photovoltaic power generation, and provides information for the thermal management strategies of related chalcogenides and materials with high saturated vapor pressure.