Photoelectrochemical Performance Observed in Mn-Doped BiFeO₃ Heterostructured Thin Films

Pure BiFeO₃ and heterostructured BiFeO₃/BiFe_0.95Mn_0.05O₃ (5% Mn-doped BiFeO₃) thin films have been prepared by a chemical deposition method. The band structures and photosensitive properties of these films have been investigated elaborately. Pure BiFeO₃ films showed stable and strong response to photo illumination (open circuit potential kept -0.18 V, short circuit photocurrent density was -0.023 mA·cm^-2). By Mn doping, the energy band positions shifted, resulting in a smaller band gap of BiFe_0.95Mn_0.05O₃ layer and an internal field being built in the BiFeO₃/BiFe_0.95Mn_0.05O₃ interface. BiFeO₃/BiFe_0.95Mn_0.05O₃ and BiFe_0.95Mn_0.05O₃ thin films demonstrated poor photo activity compared with pure BiFeO₃ films, which can be explained by the fact that Mn doping brought in a large amount of defects in the BiFe_0.95Mn_0.05O₃ layers, causing higher carrier combination and correspondingly suppressing the photo response, and this negative influence was more considerable than the positive effects provided by the band modulation.