Honeycomb-like organized TiO₂ photoanodes with dual pores for solid-state dye-sensitized solar cells

A solid-state dye-sensitized solar cell (ssDSSC) with 7.4% efficiency at 100 mW/cm² is reported. This efficiency is one of the highest observed for N719 dye. High performance is achieved via a honeycomb-like, organized mesoporous TiO₂ photoanode with dual pores, high porosity, good interconnectivity, and excellent light scattering properties. The TiO ₂ photoanodes are prepared without any TiCl₄ treatment via a one-step, direct self-assembly of hydrophilically preformed TiO₂ nanocrystals and poly(vinyl chloride)-g-poly(oxyethylene methacrylate) (PVC-g-POEM) graft copolymer as a titania source and a structure-directing agent, respectively. Upon controlling the secondary forces between the polymer/TiO₂ hybrid and the solvent by varying the amounts of HCl/H₂O mixture or toluene, honeycomb-like structures are generated to improve light scattering properties. Such multifunctional nanostructures with dual pores provide good pore-filling of solid polymer electrolyte with large volume, enhanced light harvesting and reduced charge recombination, as confirmed by reflectance spectroscopy, incident photon-to-electron conversion efficiency (IPCE), and electrochemical impedance spectroscopy (EIS) analysis.