Mesoscopic TiO 2 /Nb 2 O 5 Electron Transfer Layer for Efficient and Stable Perovskite Solar Cells

There has been tremendous advancement in the field of perovskite photovoltaics by means of interfacial engineering, compositional engineering and optimization of charge collection efficiency. The large bandgap oxides deposited using atomic layer deposition (ALD) technique have proven to be successfully passivating the interfacial defects owing to the advantages offered by this technique. Here, the effect of surface modification of mesoporous TiO 2 (ms‐TiO 2 ) layer with a transition metal oxide named niobium pentoxide (Nb 2 O 5 ) deposited by ALD technique on the performance and stability of perovskite solar cells (PSCs) is investigated. The results reveal that functionalization with ultrathin Nb 2 O 5 layer improve the optoelectronic properties and morphology of the deposited perovskite films. Moreover, the charge transfer is improved and hence the interfacial recombination is reduced. This results in improved power conversion efficiency (PCE) from 19.11% to 21.04% and open‐circuit voltage ( V OC ) from 1.118 to 1.147 V for the modified champion device. Additionally, the device shows negligible hysteresis with enhanced shelf life thermal and UV stabilities.