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

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. • An effective material model for type-II GaAsSb/GaAsN superlattices is calibrated via drift-diffusion simulations. • Excellent agreement between simulation and experimental device performance is demonstrated. • A higher carrier mobility in short period superlattices as compared to bulk and thick period superlattices explains the improved solar cell performance. • An absorber thickness between 250 and 500 nm is identified as an optimal trade-off between light absorption and carrier extraction efficiency. • An enhancement of 2.74 % in power conversion efficiency is experimentally confirmed when reducing the superlattice thickness from ∼1 μm to 250 nm.