Optimization of electrical and photovoltaic properties of Au-BiFeO<sub>3</sub> nanocomposite films

Abstract

Ferroelectric films, are an important class of photoelectric functional material, which possess the following characteristics: the breaking of their symmetry can lead to self-polarization and this polarization state can be regulated by external stimuli. The photovoltaic properties of ferroelectric films have been extensively investigated due to their potential applications in the field of photodetection, energy conversion harvesting and nonvolatile storage. In view of the small photocurrent density and the degradation of photovoltaic property caused by the depolarization effect in ferroelectric films, it is necessary to explore an approach to improving the self-polarization phenomenon and regulating the conduction mechanism to further optimize their photovoltaic properties. Here in this work, BiFeO<sub>3</sub> (BFO) films dispersed with Au nanoparticles are deposited on FTO glass substrates by the sol-gel method to obtain the Au-BFO nanocomposite films. Moreover, the relationships between Au content (0 mol%, 0.25 mol%, 0.5 mol%, 1 mol% and 3 mol%) and microstructure, electrical and photovoltaic properties of Au-BFO nanocomposite films are investigated to determine the optimal Au content. Piezoresponse force microscopy studies show that the Au-BFO nanocomposite film with 0.5 mol% Au has the strong self-polarization phenomenon. With the increase of Au content, the conduction mechanism of the Au-BFO nanocomposite films is described by the space-charge limited current theory but not the Schottky emission model any more. The photovoltaic properties of the Au-BFO nanocomposite films first increase and then decrease. When Au content is 0.5 mol%, the Au-BFO nanocomposite film has the best photovoltaic property. The open-circuit voltage and short-circuit photocurrent density of the Au-BFO nanocomposite film with 0.5 mol% Au increase nearly 3 and 5 times counterparts of the BFO film, respectively. The photovoltaic effects of Au-BFO nanocomposite films are improved mainly by regulating the self-polarization phenomenon and conduction mechanism. This study demonstrates the merits of BFO films dispersed with Au nanoparticles, specifically, the photovoltaic properties of Au-BFO nanocomposite films are further optimized. In this work, we propose a simple and effective method to regulate the electrical and photovoltaic properties of ferroelectric films, which provides a new perspective for further understanding the photovoltaic effects of ferroelectric films.