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

Inorganic CsPbBr 3 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-TiO 2 ) has been widely used as electron-transporting layer (ETL) material for inorganic CsPbBr 3 PSC. However, c-TiO 2 requires high-temperature (>450 °C) fabrication process which impedes the application of flexible inorganic CsPbBr 3 PSC and its low electron mobility further limits the performance enhancement. Herein, we prepared novel amorphous Nb 2 O 5 (a-Nb 2 O 5 ) ETL through a facile room-temperature sputtering method for inorganic planar CsPbBr 3 PSC. The PSC with a-Nb 2 O 5 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 Nb 2 O 5 (c-Nb 2 O 5 ) ETL or c-TiO 2 ETL by high-temperature (500 °C) annealing. The improved photovoltaic characteristic for CsPbBr 3 PSC with a-Nb 2 O 5 ETL may be ascribed to its suitable work function, high optical transmittance, low charge recombination at the a-Nb 2 O 5 /CsPbBr 3 interface and the superior crystallinity of CsPbBr 3 film deposited on a-Nb 2 O 5 ETL. Moreover, the a-Nb 2 O 5 -based CsPbBr 3 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.