Solution Processed Nb2O5 Electrodes for High Efficient Ultraviolet Light Stable Planar Perovskite Solar Cells

TiO2 is the most widely used electron transport layer (ETL) in high performance perovskite solar cells (PSCs). However, TiO2 often induces a rapid decay in performance under ultraviolet (UV) light illuminations. So, high performance ETL is urgently needed for PSCs. Here, a new kind of Nb2O5 nanoparticles ETL was developed for fabricating efficient planar PSCs with excellent UV stability. The matched band alignment between perovskites and Nb2O5 promotes electron injection at the ETL/perovskite interface, and decreases the energy barrier for electron injection. Decreased energy loss during electron transfer from perovskite to Nb2O5 and lower recombination rates in the devices contribute to the improved open-circuit voltage (Voc) of PSCs on Nb2O5 compared to devices on TiO2. Power conversion efficiency (PCE) surpassing 20% with a high Voc of 1.19 V was demonstrated for planar PSCs with Nb2O5 ETL. The unencapsulated devices based on Nb2O5 retained 93% of their initial short-circuit current density (Jsc) after 10 h exposure to concentrated 365 nm UV light (46 mW/cm2), versus 40% for devices based on TiO2, which was attributed to the excellent chemical stability nature of Nb2O5 under UV light.