Defects at the interfaces of perovskite (PVK) thin films are the main factors responsible for instability and low photoelectric conversion efficiency (PCE) of PVK solar cells (PSCs). Here, a SnO2 -MXene composite electron transport layer (ETL) is used in PSCs to improve interfacial contact and passivate defects at the SnO2 /perovskite interface. The introduced MXene regulates SnO2 dispersion and induces a vertical growth of PVK. The lattice matching of MXene and perovskite suppresses the concentration of interfacial stress, thereby obtaining a perovskite film with low defects. Compared with SnO2 -based device, the PCE of SnO2 -MXene-based device is improved by 15 % and its short-circuit current is up to 25.07 mA cm-2 . Furthermore, unencapsulated device maintained about 90 % of its initial efficiency even after 500 h of storage at 30-40 % relative humidity in ambient air. The composite ETL strategy provides a route to engineer interfacial passivation between metal halide perovskites and ETLs.
Keywords: Interfaces; MXene; Perovskite; SnO2; Solar Cells.
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