Regulation of the photovoltaic performance of TiO2@MAPbI(3) core-shell nanowire arrays

To further the exploration of perovskite nanowires, TiO2@CH3NH3PbI3 (TiO2@MAPbI(3)) core-shell nanowire arrays were successfully prepared via immersion and spin-coating methods. Because the shell thickness has a significant influence on the carrier transport capacity of nanowire arrays, different shell thicknesses were obtained by changing the precursor concentration. Subsequently, the relationship between the precursor concentration and shell thicknesses and the resulting properties of the nanowire arrays were investigated. The X-ray diffraction results showed that the prepared nanowire arrays consisted of only MAPbI(3), TiO2, and fluorine-doped tin oxide phases, with no impurities. From the scanning electron microscopy and energy dispersive X-ray spectroscopy results, the MAPbI(3) shell material was successfully coated onto the core layer of the TiO2 nanowire arrays. In addition, the average size of the core-shell nanowire arrays and the shell thickness were obtained using scanning electron microscopy and related software analyses. The results showed that the shell thickness was the largest (40 nm) when the precursor concentration was the lowest (0.025 mol L-1). Ultraviolet-visible spectroscopy showed that when the precursor concentration was 0.025 mol L-1 and the shell thickness was the largest, the nanowire array exhibited the highest absorbance and the smallest band gap, which is conducive to generating more carriers and improving its photovoltaic performance; the J-V curve showed the highest photoelectric conversion efficiency at this concentration and shell thickness. Therefore, it can be inferred that the shell thickness may affect the optical and photovoltaic properties. The relationship between the precursor concentration and thickness as well as the influence of this relationship on the properties of core-shell nanowire arrays should be further explored, to establish a foundation for the use of perovskite nanowires in the photovoltaic field.