Enhanced photovoltaic behavior of thickness-dependent BiFeO3-based heterostructures via the introduction of electron transport layers

Thickness and direct band gap are two important parameters affecting the photovoltaic performance of BiFeO3 (BFO)-based thin film. In this paper, thickness effects on the microstructure and insulating properties of BFO thin film are firstly explored. The minimum leakage current density (2.18x10(-5) A/cm(2) at 200kV/cm) of 200nm thin film is obtained due to a well-crystallized polycrystalline structure with high densification. On the basis, FTO/TiO2/BFO and FTO/ZnO/BFO heterostructures are proposed and successfully prepared. It turns out that with the introduction of TiO2 and ZnO acting as electron transport layer, both heterostructures possess enhanced absorption intensity and exhibit a significant red-shift, which can be ascribed to the reduced direct band gap (E-g) of 2.66 and 2.63eV, respectively. Particularly, ZnO/BFO possess enhanced photovoltaic with relatively large V-oc, J(sc), FF and values of 1.32V, 3.63mA/cm(2), 0.59 and 2.86, respectively. Our results demonstrate that the introduction of electron transport layer tends to be an effective way in improving the photovoltaic performance of BFO-based films.