FAPbBr₃ perovskite quantum dots as a multifunctional luminescent-downshifting passivation layer for GaAs solar cells

Solar cells based on GaAs often include a wide-bandgap semiconductor as a window layer to improve surface passivation. Such devices often have poor photon-to-electron conversion efficiency at higher photon energies due to parasitic absorption. In this article, we deposit FAPbBr3 perovskite quantum dots on the AlInP window layer of a GaAs thin-film solar cell to improve the external quantum efficiency (EQE) across its entire absorption range, resulting in an 18% relative enhancement of the short-circuit current density. Luminescent downshifting from the quantum dots to the GaAs device contributes to a large effective enhancement of the internal quantum efficiency (IQE) at shorter wavelengths. Additionally, improved surface passivation of the window layer results in a 14–16% broadband increase of the IQE. These mechanisms combined with increased overall photon collection (antireflective effects) results in a doubling of the EQE in the ultraviolet region of the solar spectrum. Our results show a promising application of perovskite nanocrystals to improve the performance of well-established thin-film solar cell technologies.