LAUSR

Synergically combining their respective ultrahigh charge mobility and strong light absorption, graphene (Gr)/semiconductor heterostructures are promising building blocks for efficient optoelectronics, particularly photodetectors. Charge transfer (CT) across the heterostructure interface crucially determines device efficiency and functionality. Here we report that hole transfer processes dominate the ultrafast CT across strongly coupled double perovskite Cs2 AgBiBr6 /graphene (DP/Gr) heterostructures following optical excitation. While holes are the primary charges flowing across interfaces, their transfer direction, as well as efficiency, show a remarkable dependence on the excitation wavelength. For excitation with photon energies below the bandgap of DPs, the photoexcited hot holes in graphene can compete with the thermalization process and inject into in-gap defect states in DPs. In contrast, above-bandgap excitation of DP reverse the hole transfer direction, leading to hole transfer from the valence band of DPs to Gr. We further provide experimental evidence that increasing the excitation photon energy enhances CT efficiency for both below- and above-bandgap photoexcitation regimes, unveiling the positive role of excess energy in enhancing interfacial CT. The possibility of switching the hole transfer direction and, thus, the interfacial photogating field by tuning the excitation wavelength, provides a novel way to control the interfacial charge flow across a DP/Gr heterojunction. This article is protected by copyright. All rights reserved.