Cascade Bridge Interfacial Design for Stable and Sustainable Flexible Perovskite Solar Cells

ABSTRACT Constructing an interlayer between perovskite and zinc oxide (ZnO) electron transporting layer to passivate the implacable interfacial defects for upgrading the efficiency and stability of flexible perovskite solar cells ( f ‐PSC) is a daunting challenge and remains under explored. Herein, we present a cascade bridge interlayer strategy of zeolitic imidazole framework‐8 (ZIF‐8) at the ZnO/perovskite interface. The ZIF‐8 interlayer uplifts the work function, creating a cascade pathway and bridges through nitrogen bonding with Pb 2+ ions of perovskite, thereby facilitating electron transport and reducing interfacial charge recombination. Consequently, the ZnO surface defects are passivated by alleviating the OH ‒ species, and thus the device stability is significantly improved. The f ‐PSC with ZIF‐8 interlayer delivers a stable conversion efficiency of 17.10% with minimal hysteresis. By utilizing the piezo‐phototronic effect and subjecting the f ‐PSC to a tensile strain of 1.6%, a stable efficiency of 18.47% was achieved, representing one of the highest reported efficiencies for ZnO nanorods‐based f ‐PSC. Furthermore, the ZnO‒ZIF‐8 exhibits high adsorption capacity toward lead and traps the mobile Pb 2+ ions at the ZnO/perovskite interface, preventing the negative impact of lead leaching on environmental sustainability.