Europium ions doped WOx nanorods for dual interfacial modification facilitating high efficiency and stability of perovskite solar cells

Interface engineering is of great signification for high-performance of organic-inorganic halide perovskite solar cells (PSCs). Herein, we report a dual interface modification strategy for constructing effective and stable PSCs by simultaneously incorporating the europium ions doped WOx nanorods (Eu-WOx) into electron transport layer (ETL) and hole transport layer (HTL). A significant hysteresis-free power conversion efficiency (PCE) with 22.08%, and much better UV light/long term-stability of PSCs are achieved as compared to 19.03% for the reference one. Systematic investigations elucidate that Eu-WOx nanorods significantly contribute to the improved conductivity, carrier mobility of both SnO2 ETL and Spiro-OMeTAD HTL, and the crystalline quality of the perovskite film with the large grain size. Meanwhile, because of the perfect energy band alignment of Eu-WOx nanorods, the electrons/holes extraction efficiencies at perovskite/ETL and perovskite/HTL interfaces in PSCs are remarkably boosted. This finding highlights that Eu-WOx nanorods as the interface modifier provide a versatile avenue to construct efficient and stable PSCs for practical applications.