Enhanced performance of carbon-based planar CsPbBr₃ perovskite solar cells with room-temperature sputtered Nb₂O₅ electron transport layer

Inorganic CsPbBr₃ perovskite solar cell (PSC) has attracted much attention owing to its outstanding air and thermal stability and low cost manufacture process. Crystalline TiO₂ (c-TiO₂) has been widely used as electron-transporting layer (ETL) material for inorganic CsPbBr₃ PSC. However, c-TiO₂ requires high-temperature (>450 °C) fabrication process which impedes the application of flexible inorganic CsPbBr₃ PSC and its low electron mobility further limits the performance enhancement. Herein, we prepared novel amorphous Nb₂O₅ (a-Nb₂O₅) ETL through a facile room-temperature sputtering method for inorganic planar CsPbBr₃ PSC. The PSC with a-Nb₂O₅ ETL has gained a champion efficiency of 5.74%, which is higher than that of the PSC (5.12% or 4.67%) based on crystalline Nb₂O₅ (c-Nb₂O₅) ETL or c-TiO₂ ETL by high-temperature (500 °C) annealing. The improved photovoltaic characteristic for CsPbBr₃ PSC with a-Nb₂O₅ ETL may be ascribed to its suitable work function, high optical transmittance, low charge recombination at the a-Nb₂O₅/CsPbBr₃ interface and the superior crystallinity of CsPbBr₃ film deposited on a-Nb₂O₅ ETL. Moreover, the a-Nb₂O₅-based CsPbBr₃ PSC without encapsulation exhibits a good long-term stability in ambient atmosphere. This work offers a new research direction for preparing high-performance inorganic PSC.