Manipulation of Oxygen Vacancy for High Photovoltaic Output in Bismuth Ferrite Films
Very recently, the ferroelectric photovoltaic property of bismuth ferrite (BiFeO3, BFO) has attracted much attention. However, the physical mechanisms for its anomalous photovoltaic effect and switchable photovoltaic effect are still largely unclear. Herein, a novel design was proposed to realize a high photovoltaic output in BiFeO3 films by manipulating its oxygen vacancy concentration through the alteration of the Bi content. Subsequent results and analysis manifested that the highest photovoltaic output was achieved in Bi1.05FeO3 films, differing 1000 times from that of Bi0.95FeO3 films. Simultaneously, the origin of photovoltaic effect in all BiFeO3 films was suggested as the bulk photovoltaic mechanism instead of the Schottky effect. Moreover, oxygen vacancy migration should be the dominant factor determining the switchable photovoltaic effect rather than the ferroelectric polarization. A switchable Schottky-to-Ohmic interfacial contact model was proposed to illustrate the observed switchable photovoltaic or diodelike effect. Therefore, the present work may open a new way to realize the high power output and controllable photovoltaic switching behavior for the photovoltaic applications of BiFeO3 compounds.