Illumination-driven energy level alignment at interfaces between metal halide perovskites and organic semiconductors Fengshuo Zu 1,2 , Marcel Roß 2 , Jonathan H. Warby 3 , Martin Stolterfoht 3 , Jinzhao Li 2 , Lennart Frohloff 1 , Dongguen Shin 1 , Nir Tessler 4 , Eva Unger 2 , Steve Albrecht 2 , Norbert Koch 1,2 1 Institut für Physik & IRIS Adlershof, Humboldt-Universität zu Berlin, Germany 2 Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Germany 3 Institut für Physik und Astronomie, Universität Potsdam, Germany Understanding and controlling the energy level alignment at interfaces with metal halide perovskites (MHPs) are of high importance in order to minimize the energy losses in optoelectronic devices. Despite substantial research devoted on the fundamental optoelectronic properties, a comprehensive understanding of their electronic energy level alignment at MHPs-based interfaces is still lacking. In this contribution, we aim to provide a contemporary understanding of the energy level alignment of MHPs-based interfaces, in particular pertaining to interfaces with organic semiconductors under device operation conditions, e.g., under illumination with visible light. Upon interface formation with organic transport layers, we demonstrate that the energy levels of organic semiconductors, including the first molecular layer, exhibit huge energy-level realignment during photoexcitation. [1] This is caused by one type charge-carrier accumulation within the charge selective organic semiconductors under illumination and the weak electronic coupling between the junction components. Furthermore, analogous energy level shifts were also observed for perovskite films at the buried interface with charge-selective organic transport layers upon white light illumination. In contrast, the perovskite energy levels remain constant under illumination when a charge nonselective substrate is employed. [2] The fact that the interfacial energy level alignment at MHPs-based junctions under illumination can differ from that in dark is to be taken into account in order to fully rationalize device characteristics. References 1. F. Zu, J. H. Warby, M. Stolterfoht, J. Li, D. Shin, E. Unger, N. Koch, Phys. Rev. Lett. 2021, 127, 246401. 2. F. Zu, M. Roß, L. Frohloff, D. Shin, N. Tessler, S. Albrecht, N. Koch, Sol. RRL 2022, 2101065, 2101065.
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