Publication | Open Access
The Performance and Stability of Ambient Temperature Molten Salts for Solar Cell Applications
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1996
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EngineeringElectrode-electrolyte InterfaceEnergy ConversionThermal Energy StorageChemistryPhotovoltaicsMass TransportChemical EngineeringOrganic SolventsThermophysicsThermodynamicsSolar Thermal EnergySolar Energy UtilisationMaterials ScienceElectrical EngineeringEnergy StorageElectrochemical ProcessEnergy MaterialElectrochemistrySolar Cell ApplicationsSensitizer TurnoverBatteriesThermal EngineeringThermophysical PropertySolar Cell Materials
Room‑temperature molten salt systems based on methyl‑hexyl‑imidazolium iodide (MHImI) are used to study performance, stability, and mass‑transfer effects in photoelectrochemical regenerative devices, offering advantages over organic liquid electrolytes. The study investigates MHImI’s physical‑electrochemical properties and mixtures with organic solvents and lower‑viscosity molten salts, and uses mass‑transport simulations in nanocrystalline solar cells to illustrate concentration profiles, limiting currents, and mass‑transfer overpotentials, guiding better exploitation of molten salt electrolytes. Experimental devices demonstrate outstanding stability, with sensitizer turnover exceeding 50 million, and the practical performance confirms the beneficial impact of the investigated molten salt properties.
Room temperature molten salt systems based on methyl‐hexyl‐imidazolium iodide (MHImI) have been used to scrutinize the performance characteristics, the stability and the mass‐transfer effects in a photoelectrochemical regenerative device, as the latter is influenced and can even be limited by local concentration and mass‐transport of the electroactive redox mediator species in the electrolyte phase. These salts appear to afford particular advantages over organic liquids as solvents for solar cell electrolytes. Cell performance showed outstanding stability, with an estimated sensitizer turnover in excess of 50 million. An investigation has been carried out on the physical‐electrochemical properties of MHImI and its mixtures with organic solvents such as n‐methyl‐oxazolidinone, acetonitrile and with other lower viscosity molten salts such as methyl‐butyl‐imidazolium triflate. The repercussions of these properties on solar cells is described experimentally by the performance of practical application devices. Simulation models of mass transport in the nanocrystalline solar cell help illustrate operational aspects such as concentration profiles, limiting currents, anticipated mass‐transfer overpotential as a function of current density, and they help to make projections as to how the properties of molten salt electrolytes can be better exploited toward this practical end.