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.