ITO and electron transport layer-free planar perovskite solar cells on transparent Nb-doped anatase TiO2-x electrodes

Here, we reported on planar perovskite solar cells (PSCs) which are free of the indium tin oxide (ITO) and electron transport layer (ETL) directly prepared on Nb-doped TiO2-x (NTO) electrodes. By rapid thermal annealing of NTO film at a temperature of 600 °C under vacuum ambient, we obtained conductive anatase NTO electrodes that act as transparent electrodes and ETL simultaneously in ITO and ETL-free PSCs. The sputtered NTO electrode showed decreasing resistivity with decreasing temperature, indicating metallic conductivity. A planar NTO∖(FAPbI3)1-x(MAPbBr3)x∖Spiro-MeOTAD∖Au cell showed a power conversion efficiency of 12.50% and open-circuit voltage of 1.08 V in spite of the absence of ETL. The ITO and ETL-free PSC with an NTO electrode exhibited a higher open-circuit voltage of 1.08 V than did an ETL-free PSC with ITO electrode because of effective hole blocking by the NTO electrodes. Our results suggest that sputtered NTO film is a promising multi-functional electrode acting as ETL and transparent electrode simultaneously for achieving simply fabricated and cost-effective PSCs. [Display omitted] •Nb-doped anatase TiO2-x (NTO) film which act as ETL and cathode simultaneously in perovskite solar cells (PSCs) is investigated.•The effect of film thickness on the electrical, optical, structural and morphological properties of NTO electrodes is analyzed.•The ETL and ITO-free PSC fabricated on 300 nm-thick NTO electrode exhibits the average PCE of 12.50%.