Greatly enhanced photocurrent density in bismuth ferrite films by Localized Surface Plasmon Resonance effect

Very recently, the ferroelectric photovoltaic effect of multiferroic BiFeO₃ (BFO) has attracted much attention because of its large photovoltage beyond the bandgap and unique photocurrent switchable characteristics. However, the poor short-circuit current density (J_SC ∼ μA/cm²) of BFO leads to a low power conversion efficiency (PCE), which greatly hinders its application and development as photovoltaic or optoelectronic devices. In this paper, a novel heterostructure comprised Au nanoparticles layer and BiFe_0.9375Mn_0.0625O₃ (BFMO) thin film was constructed. The results and analysis showed that the photocurrent densities of all these heterostructures were greatly improved in comparison with that of pure BFMO film without Au layer. Especially, the maximum photocurrent density of 1.323 mA/cm² was observed in the heterostructure of BFMO-Au-1 m, which is 50 times higher than that of pure BFMO film (26 μA/cm²). A possible mechanism was herein proposed that the Localized Surface Plasmon Resonance (LSPR) effect derived from Au nanoparticles might play a key role on the enhanced photocurrent densities of these heterostructures. Firstly, LSPR effect would effectively amplify the intensity of the incident light partially passing through BFMO film and then reentering the film through the diffuse reflection, which greatly enhance the light absorption of the film. Secondly, the locally strengthened electric field around Au nanoparticles greatly enhances the migration rate of surrounding electrons, and thus improves the separation efficiency of electron-hole pairs. Consequently, the photocurrent density of BFMO film was greatly enhanced by LSPR effect.