Continuous electron transport pathways constructed in TiO2 sub-microsphere films for high-performance dye-sensitized solar cells

摘要

TiO2 sub-microspheres applied as photoanodes in dye-sensitized solar cells (DSSCs) have been reported to have dual functions with high specific surface areas and light scattering capabilities. Large voids are left in the sub-microsphere film and lead to the poor connectivity between the neighboring sub-microspheres, which will limit the enhancement of the short-circuit current density (J(SC)) and the power conversion efficiency (h). Herein, we develop a closely linked network by introducing TiO2 nanocrystallines into the voids to construct a continuous electron transport pathway. It is found that pore sizes, porosity, and specific surface area could be effectively tuned by simply adjusting the content of TiO2 nanocrystallines. As confirmed by the intensity-modulated photocurrent/photovoltage spectroscopy (IMPS/IMVS) and electrochemical impedance spectra (EIS), when the content of TiO2 nanocrystallines in the sub-microspheres is 10 wt% (NP10), the electron transport time, electron collection efficiency, and electron diffusion length are optimized compared with the other contents. As a result, the eta of the optimized NP10 photoanode based DSSC is up to 11.22%, which is higher than the 10.58% efficiency demonstrated by the pure sub-microsphere photoanode based cell.