Sputtering of TiO₂ for High-Efficiency Perovskite and 23.1% Perovskite/Silicon 4-Terminal Tandem Solar Cells

Radio frequency (RF) magnetron-sputtered TiO2 (RS-TiO2) is investigated as a hole-blocking layer for perovskite solar cells. RS-TiO2 shows conformal, dense, and efficiently electron transferable properties. Power conversion efficiency (PCEs) of 20.9% were obtained with high reproducibility. RS-TiO2 also showed potential in the up-scaling process, transparent perovskite, and perovskite/silicon 4-terminal tandem solar cells. With increasing active area 40 times from 0.075 cm2 to 3 cm2 without dividing areas by laser patterning, less than 4% open-circuit voltage (Voc) and short-circuit current density (Jsc) drops were observed. This means RS-TiO2 layers can maintain their film quality even when the area size is increased. Furthermore, by applying RS-TiO2 to transparent perovskite solar cells and perovskite/silicon 4-terminal tandem solar cells, PCEs of 16.7% and 23.1% were obtained, respectively.