Quasi-Solid-State Dye-Sensitized TiO₂ Solar Cells:  Effective Charge Transport in Mesoporous Space Filled with Gel Electrolytes Containing Iodide and Iodine

Abstract

Quasi-solid-state dye-sensitized solar cells were fabricated using low-molecular-weight gelators. They showed comparable photoenergy conversion efficiencies to the liquid cell at high illumination intensity up to AM 1.5 (1 sun). Conductivity measurements of the electrolyte phases revealed that the gelation does not affect the conductivity of the electrolyte and that the conductivity increased with an increase of iodine in both gel electrolytes and liquid electrolyte. The formation of polyiodide ions, such as I3 - and I5 -, caused by addition of iodine was confirmed by Raman spectroscopic measurement. The self-diffusion of iodide species in the gel electrolyte was found about a quarter of that of I- in acetonitrile. The formation of less-mobile polyiodide ions in electrolyte increased the conductivity in the mesoporous phase, which should be rationalized as due to the Grotthuss-type electron exchange mechanism caused by rather packed polyiodide species in the electrolytes. The optimized quasi-solid-state cell showed the values of 0.67 V for open-circuit voltage, 12.8 mA cm-2 for short-circuit photocurrent density, and 5.91% for photoenergy conversion efficiency under AM 1.5 irradiation with higher durability.

Conduction Through Viscoelastic Phase in a Redox‐Active Ionic Liquid at Reduced Temperatures

“…[19,20] Previously it was found that incorporating the redox couple I /I 3 and higher polyidides into existing gel electrolytes by adding iodine increases the conductivity, which was attributed to Grotthuss conduction. [21,22] However, by adding iodine to the ). b) The liquid, viscoelastic and crystalline phases are indicated on the figure for decreasing temperatures.…”

Application of a composite polymer electrolyte based on montmorillonite in dye-sensitized solar cells

“…To overcome these problems, many research groups have been searching for alternatives to replace the liquid electrolytes, such as inorganic or organic hole conductors, 2-4 ionic liquids, 5,6 polymer 7-9 and gel electrolytes. [10][11][12][13][14] Our group has been working on DSSC using polymer electrolytes based on copolymers of poly(ethylene oxide) (PEO) derivatives since 1996 and the first results were published in 1999. 15 The best solar energy conversion efficiency obtained for a solid-state DSSC (1 cm 2 of active area) was 2.6% under 10 mW cm -2 and 1.6% under 100 mW cm -2 .…”

Influence of Iodide Concentration on the Efficiency and Stability of Dye‐Sensitized Solar Cell Containing Non‐Volatile Electrolyte

“…Diffusion by a physical and bond exchange (Grotthuss) mechanism has been proposed to occur in electrolytes containing the I À /I 3 À redox couple. [13] When both simple physical diffusion and exchange reaction are present, D app can be rationalized by the Dahms-Ruff Equation (1): [14][15][16][17][18] …”