Thin-film Solar Cells with MgF2/Ag back mirror patterning for improved near-IR reflectance

Abstract

Combining epitaxial lift-off with a dielectric-metal back mirror boosts III-V solar cells efficiencies without sacrificing the costly growth wafer. In this work, GaAs and GaInP/GaInAs solar cells are produced with a patterned $\mathbf{MgF}_{2}/\mathbf{Ag}$ mirror. The sub-bandgap reflectance increases by 3.0% and 2.6%, respectively, compared to the devices with a full Ag back mirror. Initial results indicate that, during operation, the temperature-induced open-circuit voltage degradation decreases due to the enhanced reflection of unused near-infrared photons.