Simulation, optimization, and experimental validation of 1eV GaAsSb/GaAsN superlattice solar cells

Abstract

Increasing demand for highly efficient solar cells drives the development of advanced materials for next- generation devices. While multi-junction solar cells address fundamental performance limits such as absorption and thermalization losses, improving efficiency with monolithic structures further requires novel materials with the necessary bandgap energies and lattice parameters. We have recently proposed the GaAsSb/GaAsN superlattice (SL) system as a promising material candidate; however, the performance of the devices is still well below their potential. In this work, drift-diffusion models are calibrated and used for parameter extraction, which allows to identify mobility and lifetime as key performance bottlenecks for carrier collection. By optimizing the device structure, it is found that SLs with absorber thicknesses in the range from 250 nm to 500 nm offer the best performance, balancing absorption and charge extraction, with the power conversion efficiency increasing by a factor of four compared to thicker devices. The findings lay the groundwork for further improvements of the GaAs(Sb)(N) material system in thin-film and multi-junction solar cell applications.