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 TiO 2 (c-TiO2) has been widely used as electrontransporting layer (ETL) material for inorganic CsPbBr3 PSC. However, c-TiO2 requires high-temperature ( > 450 degrees 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.