Facile Deposition of Nb₂O₅ Thin Film as an Electron-Transporting Layer for Highly Efficient Perovskite Solar Cells

In a typical high-performance perovskite solar cell (PSC), the electron-transporting layer (ETL) plays a critical role in facilitating the transportation of the photogenerated carriers from perovskite to electrode. In the present work, the solution-processed Nb2O5 film is successfully prepared to serve as an alternative for replacing the overwhelmingly dominated TiO2 ETL with a facile deposition approach. By adjusting the spin-coating process of the precursor solution, the best power conversion efficiency of 19.2% is achieved in the Nb2O5-based planar PSC when the thickness of C–Nb2O5 ETL is about 100 nm. The characterization including ultraviolet photoelectron spectroscopy, electronic impedance spectroscopy, and photoluminescence spectrum results elucidate that the impressive photovoltaic performances can be attributed to the proper Nb2O5 ETL conductive band, the lower charge recombination rate, the more efficient extraction, and transportation of the photogenerated carriers from the perovskite absorber.