Enhanced Photovoltaic Performance of Sol–gel-Derived FTO/TiO2/BiFeO3 Heterostructure Thin Film Obtained Via Modifying Thickness of TiO2 Transport Layer

BiFeO3 (BFO) is a promising photovoltaic material and TiO2 tends to be an efficient electronic transmission material in perovskite solar cells. In this paper, FTO/TiO2/BFO heterostructure thin films with various TiO2 thicknesses (0, 50, 100, and 150 nm, respectively) are prepared successfully via a sol–gel method. The effects of TiO2 layer thickness on the microstructure, insulating and photovoltaic properties are characterized. All the thin films possess a polycrystalline structure that matches well with the perovskite phase. Significant improvement can be achieved with the introduction of the TiO2 electron transport layer. Among all tested films, the one with 100 nm-TiO2 exhibited superior photovoltaic performance. The champion power conversion efficiency (η) of 3.67% with fill factor of 0.64 could be achieved with an open-circuit voltage (Voc) of 1.64 V and a short-circuit photocurrent (Jsc) of 3.50 mA/cm2. This can be ascribed to the favorable effect of TiO2 to the electron transport and restriction to the electron–hole recombination.