Role of domain walls in the abnormal photovoltaic effect in BiFeO 3

Abstract

Recently, the anomalous photovoltaic (PV) effect in BiFeO 3 (BFO) thin films, which resulted in open circuit voltages (V oc) considerably larger than the band gap of the material, has generated a revival of the entire field of photoferroelectrics. Here, via temperature-dependent PV studies, we prove that the bulk photovoltaic (BPV) effect, which has been studied in the past for many non-centrosymmetric materials, is at the origin of the anomalous PV effect in BFO films. Moreover, we show that irrespective of the measurement geometry, V oc as high as 50 V can be achieved by controlling the conductivity of domain walls (DW). We also show that photoconductivity of the DW is markedly higher than in the bulk of BFO.