The improvement of open circuit voltage by the sputtered TiO2 layer for efficient perovskite solar cell

•High performance planar perovskite solar cell is prepared based on the compact TiO2 films grown by RF sputtering.•A high open circuit voltage of about 1.03 V can be obtained as compared to 0.92 V of solution based TiO2.•Nearly 100% coverage of perovskite film on sputtered TiO2 can be observed using the one step method.•The full coverage and the proper band alignment are two reasons responsible for the high open circuit voltage.

The uniform and compact n-type TiO2 window layers were prepared by RF sputtering using a TiO2 ceramic target. A high open circuit voltage of about 1.03 V with the efficiency of 13.23% can be obtained as compared to 0.92 V of solution based TiO2. Nearly 100% coverage of perovskite film on sputtered TiO2 can be observed in the scanning electron microscopy images, obviously higher than 92% coverage on solution-based TiO2. The full coverage of perovskite and the proper band alignment between sputtered TiO2 and spiro-OMeTAD are two reasons responsible for the high open circuit voltage. The effects of annealing, growth temperature, sputtering target and thickness on performance of solar cell are also discussed.