**4. Conclusions**

**Figure 4.** (a) The schematic diagram of the experimental configuration. The photocurrent was measured with the negative electrode connected with the central electrode and the positive electrode connected with the outer electrodes. *θ* is defined as the angle between the linearly polarized light and the plane of the sample along *x* axes, i.e., the (100) direction. Photocurrent measured at different angles, with the direction of the current flow along [-110] direction (b), [1-10] direction (c), [110] direction (d) and [-1-10] direction (f). The solid line represents the fit with Eq. (2).

16 Ferroelectrics and Their Applications

Tetragonal BiFeO3 films with the thickness of 30 nm were grown epitaxially on (001) oriented LaAlO3 substrate by using pulsed laser deposition (PLD) and the photovoltaic effect of tetragonal BiFeO<sup>3</sup> along different crystallographic direction with in plane symmetric electrodes was investigated, the absorption onset and the direct band gap are ~2.25 and ~2.52 eV, respectively. The photocurrent exhibits definitive angular and direction dependency, indicating obvious bulk photovoltaic effect and depolarization field effect. The photocurrent depends not only on the sample directions in-plane but also on the angle between the linearly polarized light and the plane of the sample along *X* and *Y* directions. The polarization direction is along [110] direction and the photocurrent induced by this depolarization field is as large as ~3.53 μA/cm2 , while the BPV induced photocurrent can be described as *Jx* ≈ 2.23cos(2*θ*), such an angular dependence of photocurrent is produced as a consequence of asymmetric microscopic processes of carriers such as excitation and recombination. These results indicate that the BPV and depolarization field effect in tetragonal BiFeO3 thin films could be further explored for the next generation of solar photovoltaic applications.
