Solid-state dye-sensitized hierarchically structured ZnO solar cells

► A novel hierarchically structured ZnO solid-state DSC is fabricated. ► The electrolyte containing PEO/PEG/TiO 2/LiI/I 2 possesses a high ionic conductivity. ► Under optimal composite electrolyte the cell performance is improved. A novel solid-state hierarchically structured ZnO dye-sensitized solar cell (DSC) was assembled by using TiO 2 as filler in polyethylene oxide (PEO)/polyethylene glycol (PEG) electrolytes and ZnO nanocrystalline aggregates as photoanode film. Under optimized composite polyelectrolyte containing PEO/oligo-PEG/TiO 2/LiI/I 2 the photovoltaic performance of the solid-state ZnO DSCs was significantly better, with an overall conversion efficiency ( η) of 1.8% under irradiation of 100 mW/cm 2, which was higher than those of the cells with PEO/TiO 2/LiI/I 2 ( η = 1.1%) or PEO/oligo-PEG/LiI/I 2 electrolyte ( η = 1.5%). Further, the hierarchically structured ZnO-based cell showed a higher η value of 2.0% under 60 mW/cm 2 radiation. The morphologies, ionic conductivity of three different composite electrolytes and their performance to the DSCs were also studied by FESEM, I– V data, IPCE and EIS.