Employment of Charge Transport Layers in Bismuth Ferrite Ferroelectric Photovoltaic Cells for Achieving High Power Conversion Efficiency
Zehao Sun, Jie Wei, Youxin Yuanfeng, Ao Cao, Junlong Zhang, Xuyu Shen
Abstract
As a classical multiferroic material with strong photoinduced and iron-polarized coupling, bismuth ferrite (BiFeO 3 ) might offer an approach to creating reliable and effective photovoltaic systems in the future. A novel ferrielectric photovoltaic device of FTO/Au-NPs/TiO 2 /BSFCO-g/NiO on the basis of a (Sm, Co)-gradient-doped BiFeO 3 thin film (BSFCO-g) was well designed and fabricated in this study. First, an Au nanoparticles (Au-NPs) layer was deposited between FTO substrate and BSFCO-g thin film, where localized surface plasmon resonance (LSPR) effect was introduced to enhance the separation of photogenerated carriers and improve the light absorption of BSFCO-g film. Gradient doping introduced oxygen vacancy gradient distribution and flexoelectric effect into BSFCO-g film, in which two built-in electric fields were induced to speed up the separation of photogenerated carriers. Finally, TiO 2 and NiO as electron and hole transport layers were introduced into the device’s structure so as to inhibit electron–hole recombination and improve the collection efficiency of charges. Through the coupling effect of all of the above factors, the BiFeO 3 -based ferroelectric photovoltaic device obtained extremely excellent photovoltaic characteristics. For instance, the short-circuit current density ( J SC ) is over 9.45 mA/cm 2 and open circuit voltage ( V OC ) goes up to 1.83 V (light source, laser with a wavelength of 405 nm and a power density of 50 mW/cm 2 ). Especially, the power conversion efficiency (PCE) of this device reaches a staggering 15%, which is much higher than those of ferroelectric photovoltaic devices reported previously. It is believed that the achievements in this work will greatly promote the process of ferroelectric photovoltaic devices toward commercial applications.