High-efficiency quasi-solid state dye-sensitized solar cells using a polymer blend electrolyte with “polymer-in-salt” conduction characteristics

Abstract

Abstract “Polymer-in-salt” electrolytes are special conductive materials that demonstrate much higher conductivity compared to the conventional “salt-in-polymer” electrolytes. However, up-to-now, they are found unsuitable for dye-sensitized solar cells (DSSCs) application, mainly because they lead to increased charge recombination rate. The present paper demonstrates the development and application in DSSCs of polymer blend electrolytes that utilize features found in “polymer-in-salt” electrolytes, while the aforementioned drawback is overcome. This is done with the appropriate selection and amount of polymers used to jellify the liquid state electrolyte, keeping the redox couple concentration fixed at a high level. Herein, the unique properties of polyvinylpyrrolidone (PVP), as a nitrogen-containing heterocyclic polymer, in combination with the ability of polyethylene glycol (PEG) to dissolve high quantities of ionic compounds, were the main reasons for developing PVP/PEG blend-based polymer electrolytes for DSSCs. The efficiency attained by the solar cells employing the polymer blend electrolytes was found enhanced up to 30% compared to the corresponding of DSSCs employing the PVP-based and PEG-based polymer electrolytes. By the extra use of two common additives in the best-performing polymer blend electrolyte and an advanced multi-layered photo-anode, the efficiency of DSSCs reached 8.21%, which is one of the highest reported for quasi-solid state DSSCs employing non-composite ionic liquid-free iodide-based polymer electrolytes. The results are also found quite satisfactory compared to the corresponding ones obtained by the DSSCs employing commercially available liquid state electrolytes, while the preparation of the proposed electrolytes is simple and of low-cost, and their composition has great prospects for further improvement.