Improved performance of TiO2 nanoarray/BiOI heterojunction all-solid-state solar cells by incorporating BiFeO3 perovskite interlayer

The photovoltaic conversion of heterojunction solar cells relies on the interface properties between n-type and p-type semiconductors. N-type TiO 2 -nanoarray (NA), ferroelectric BiFeO 3 interlayer, and p-type BiOI were used to fabricate a ternary bulk heterojunction using a solution-based method in this study. Solid-state solar cells of FTO/TiO 2 -NA/BiFeO 3 /BiOI/spiro-OMeTAD/Ag are constructed for the first time, and their photo-electric conversion performance is studied. The addition of a BiFeO 3 interlayer at the interface between TiO 2 -NA and BiOI increased the solar cell open-circuit voltage ( V oc ) from 0.18 to 0.47 V and the short-circuit current ( J sc ) from 0.29 to 0.54 μA/cm 2 , resulting in a nearly 5-fold increase in power conversion efficiency. The Kelvin Probe force microscope analysis confirmed that the polarization electric-field ( E self ) generated by the BiFeO 3 interlayer is directed toward BiOI, thereby increasing the surface potential and decreasing electron and hole back flows between TiO 2 and BiOI. This additional electric field caused greater charge concentrations and a greater V oc . Furthermore, the E self directed toward the BiOI increased the built-in electric field ( E bi ) in the space charge area from TiO 2 to BiOI, allowing for greater separation of photogenerated electrons and holes and thus raising the J sc . The findings of this study suggested that manipulating internal electric fields via polarization could be an effective method for enhancing the performance of solar cells based on BiOI.