Rapid I⁻/I₃⁻ Diffusion in a Molecular‐Plastic‐Crystal Electrolyte for Potential Application in Solid‐State Photoelectrochemical Cells

Abstract

High current‐carrying capacity and rapid, liquidlike diffusion were achieved in a dye‐sensitized solar cell (DSSC) based on the plastic‐crystalline electrolyte succinonitrile and the I−/I3− redox couple (see diagram). This could lead to the development of true solid‐state DSSCs without conventional organic‐liquid electrolytes, which can cause problems with long‐term device stability.

Molecular diffusion and dc conductivity perfectly correlated with molecular rotational dynamics in a plastic crystalline electrolyte

“…15 As pointed out earlier, the value of σ dc of plastic SN and dinitrile mixtures is surprisingly high. A likely explanation for the relatively high σ dc values is that they are due to a minority of dinitrile molecules present as molecular ions.…”

“…Upon doping the mixture with LiBF 4 , the dc conductivity increased due to the higher ion density. [13][14][15] The characteristic frequency of the relaxation is lower in the doped mixture (especially at low T) due to the stronger interactions induced by the presence of Li + and BF 4 -ions. 31 Also the dc conductivity values are quite different: not only is σ dc higher when Li + ions are present, but it also spans a larger number of decades between 240 and 160 K (instead, the relaxation frequency spans a smaller number of decades, in a given temperature interval, when Li + ions are present).…”

Plastic–polymer composite electrolytes for solid state dye-sensitized solar cells

“…In general, the plastic-polymer electrolytes displayed an ambiguous conductivity-temperature relationship, which obeys neither the classical Arrhenius law for liquid electrolytes nor the free-volume law (Vogel-Tammann-Fulcher model) for polymer electrolytes. The log − T −1 profiles for all the SCNplasticized iodide polymers appeared most likely in a similar fashion as plastic crystal electrolytes [11,16].…”

“…In the pursuit of solvent-free electrolytes for solid state DSSCs, soft matter electrolytes, such as polymers [5][6][7], ionic liquids [8,9] and plastic crystal electrolytes [10][11][12], seem to be a good choice of the candidate electrolytes for DSSC applications because of their appropriate ionic conductivity and electrochemical compatibility. However, the pure polymer electrolytes reported so far have usually an insufficient ambient ionic conductivity and poorer contact with the nanocrystalline photoelectrodes, the DSSCs with such electrolytes have yet achieved a photoconversion efficiency of ∼5%, about a half of the photoconversion efficiency of the DSSCs using organic liquid electrolytes.…”

Fabrication of Stable Dye Sensitized Solar Cell with Gel electrolytes Using Poly(ethylene oxide)-Poly(ethylene glycol)

“…Hence, the photoconversion efficiency of DSSCs with liquid electrolytes deteriorates gradually. Several attempts have been made for the replacement of liquid electrolytes in DSSC by using polymer gel electrolytes [4,5], room temperature ionic liquids [6,7], organic [8,9] and inorganic p-type semiconductors [10][11][12][13] as a hole transporting materials.…”