Dye-Sensitized Solar Cells Based on a New Type of Non-Volatile Co(II)/Co(III) Electrolyte Delivering Higher Power Conversion Efficiency for Indoor Applications

Background: Electrolyte is an essential constituent of a dye-sensitized solar cell (DSSC) as it mediates charge transport and regenerates the oxidized dye. Iodide/triiodide (I-/I^3-) based electrolytes are the ones widely being used in DSSCs. These types of electrolytes are usually made by dissolving high concentrations of triiodide and polyiodide species in solvents, such as acetonitrile and methoxypropionitrile. These solvents face evaporation issues and lead to stability problems, which reduces the life span of the DSSC. For solving these issues, various types of electrolytes, such as ionic liquids and gelated liquid electrolytes, have been used to replace conventional volatile electrolytes. Objective: To solve the solvent evaporation issue and the electrical resistance rise, we aim to synthesis a non-volatile electrolyte with excellent open-circuit voltage and stability. Methods: A new genre of nonvolatile Co(II)/Co(III) redox electrolyte was synthesized by the reaction of tris(2-(1H-pyrazol-1-yl)pyridine)cobalt(II) and tris(2-(1H-pyrazol-1-yl)pyridine) cobalt(III) with 2,4,6-tris(dodecyloxy)benzaldehyde. As a proof-of-principle experiment, a DSSC was fabricated using the as-synthesized electrolyte, N-719 dye as the light harvester, and TiO2 as the photoanode, and their performances were analyzed in room light conditions. Results: The DSSCs deliver a remarkable power conversion efficiency of 22.1%, an open circuit voltage of 1 V, and a power output of 88.5 μW cm^–2 at 1000 lux, under illumination from a Deltron LED light. Conclusion: Cobalt-based non-volatile electrolytes are efficient candidates that can replace the conventional volatile electrolytes in DSSCs. Further research into this new type of electrolyte could pave ways to deliver high open-circuit voltage as well as good current density with high stability.