Abstract
In this research, we prepared the undoped and doped (La, Zn) bismuth ferrite (BFO) thin films by means of sol-gel method on Pt/Ti/SiO2/Si(100) substrate. We fabricated films with different thickness by controlling the number of spin-coating layers. Furthermore, We were the first to encapsulate Au nanoparticles in the BFO films. The Au thin film was deposited by e-beam evaporation in advance, then the RTA process was treated. We found that the open-circuit voltage (VOC) varied linearly with the film thickness, and the short-circuit current density (JSC) also increased with the film thickness. The average potential drop for each domain wall is ~ 0.215 V, and the contribution of the Schottky barrier in open-circuit voltages is 0.135 V. The grains of undoped and Zn-doped BFO were both single-domain with similar grain size, while that of the La-doped BFO was multidomain with a double grain size. The VOC of the three samples were all 0.56 V. We concluded that the Fe2+ was the main defect trap center which caused recombination of carriers in the BFO photovoltaic system. The JSC of the undoped BFO was 26.4μA/cm2. La dopant raised the ratio of Fe2+/Fe3+ which lowered the JSC to 13.2 μA/cm2; in contrast, Zn dopant lowered the Fe2+/Fe3+ ratio which consequently increased the JSC to 54 μA/cm2. By encapsulating Au nanoparticles in BFO films, the exciton dissociation rate was increased by the enhanced electric field due to the surface plasmon resonance effect of Au nanoparticles. The enhancements of JSC in the sample with Au nanoparticles in the middle and near the bottom of BFO films were 18.5 % and 35.6 %, respectively.