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Hierarchical Double-Shell Nanostructures of TiO2 Nanosheets on SnO2 Hollow Spheres for High-Efficiency, Solid-State, Dye-Sensitized Solar Cells



A high-energy conversion efficiency of 8.2% at 100 mW cm−2 is reported, one of the highest values for N719-based, solid-state, dye-sensitized solar cells (ssDSSCs). The solar cells are based on hierarchical double-shell nanostructures consisting of inner SnO2 hollow spheres (SHS) surrounded by outer TiO2 nanosheets (TNSs). Deposition of the TNS on the SHS outer surface is performed via solvothermal reactions in order to generate a double-shell SHS@TNS nanostructure that provides a large surface area and suppresses recombination of photogenerated electrons. An organized mesoporous (OM)-TiO2 film with high porosity, large pores, and good interconnectivity is also prepared via a sol-gel process using a poly(vinyl chloride)-g-poly(oxyethylene methacrylate) (PVC-g-POEM) graft copolymer template. This film is utilized as a matrix to disperse the double-shell nanostructures. Such nanostructures provide good pore-filling for solid polymer electrolytes, faster electron transfer, and enhanced light scattering, as confirmed by reflectance spectroscopy, incident photon-to-electron conversion efficiency (IPCE), and intensity-modulated photocurrent spectroscopy (IMPS)/intensity-modulated photovoltage spectroscopy (IMVS).