Performance enhancement of aqueous dye-sensitized solar cells via introduction of a quasi-solid-state electrolyte with an inverse opal structure

To bridge the gap in the power conversion efficiencies (PCEs) of aqueous and organic-solvent based dye-sensitized solar cells (DSCs), water-based electrolytes are exploited for a new role to enhance DSC performance. Hydrogels with an inverse opal structure (IOS) were prepared using various SiO2 opal films as templates. The gels were further used as a host for preparing fully water-based gel electrolytes with a photonic band gap (PBG) on which quasi-solid-state DSCs were fabricated. The current voltage curves indicate that PCEs for the gel electrolytes with the IOS are superior to those for the reference gel electrolyte without the structure, and a maximum average PCE of 1.80% is achieved for the gel electrolytes with the PBG around 624 nm, which is approximately 22% higher than the value for the reference gel electrolyte (1.48%). The action spectra reveal increases of the incident photo-to-current conversion efficiencies both in and beyond the PBG region, indicating that the back reflection and scattering of photons as a result of the IOS are significant for light harvesting and PCE enhancement. The electrochemical impedance spectra further demonstrate that the IOS lowers the Warburg impedance and the resistance at the TiO2/electrolyte interface compared to the reference gel electrolyte. Furthermore, the durability of DSCs is improved by the gel electrolyte/TiO2 interface and the IOS. (C) 2016 Elsevier Ltd. All rights reserved.