Room-temperature processible TiO2 electron selective layers with controllable crystallinity for high efficiency perovskite photovoltaics

- The crystallization of the TiO2 film was finely controlled.
- Partially crystallized TiO2 film showed improved electron mobility.
- Properties of sputtered TiO2 film could be precisely controlled and reproduced.

As a remarkable wide band-gap n-type semiconductor, TiO2 has been widely used as electron selective layer in photovoltaic devices. In this work, TiO2 films with different crystallinity were deposited on FTO glass by DC magnetron sputtering at room temperature. The crystallinity of these films were controlled by precisely adjusting the sputtering power and work pressure. Taking advantages of high visible light transmittance, reduced transport resistance and effective TiO2/perovskite interface with fast electron extraction and carrier separation, high efficiency perovskite solar cells (PSCs) were assembled. The optimum crystallinity of TiO2 compact layer for PSC was defined as 26.3%. Short-circuit current density and fill factor were notably enhanced and power conversion efficiency of the device was improved to 15.76% compared with PSCs based on amorphous (13.3%) and fully crystallized TiO2 (12.9%). This research shaded light on the choice of inorganic carrier transport layers in photovoltaic devices.