Promising Surface Modification Strategies for High Power Conversion Efficiency Dye Sensitized Solar Cell Based on ZnO Composite Photoanode

Abstract

ZnO nanowires (NWs)/nanoparticles (NPs) composites grown on the indium-doped tin oxide (ITO) substrates by were used as photoanodes of dye-sensitized solar cells (DSSCs). Well-aligned ZnO NWs were synthesized by continuous flow injection (CFI) system. To increase dye absorption area, ZnO NPs were subsequently decorated on the surfaces of ZnO NWs via base-free chemical bath deposition (CBD). According to analysis of electrochemical impedance spectroscopy (EIS), the electron diffusion coefficient (Dn) inside the ZnO NWs/NPs photoanode was 3.9x10-3 cm2/s, which indicated high electron transport properties in this work. The conversion efficiency of DSSCs via D149 sensitized ZnO composite photoanode could achieve 5.24%. To furthermore increase the conversion efficiency, the surface modification process was necessary. In this study, 4-tert-butylpyridine (4-tBP) and water vapor was employed on the ZnO composite photoanodes. After treatment by 4-tBP, water molecules and applied both processes on the surfaces of ZnO NWs/NPs photoanodes, the conversion efficiencies of DSSCs could be improved from 5.25% to 5.71%, 6.30% and 6.60%, respectively. The possible enhancement mechanism could be conducted by EIS technique in this work.