Iodine-free high efficient quasi solid-state dye-sensitized solar cell containing ionic liquid and polyaniline-loaded carbon black

An incombustible and non-volatile paste with carbon black (CB), a conducting polymer (CP), and an ionic liquid (1-buty-3-methylimidazolium iodide, BMII or 1-methyl-3-propyl imidazolium iodide, PMII) was placed between the dye-sensitized porous TiO2 and the Pt counter electrode to fabricate a quasi solid-state DSSC, without the addition of iodine. While the solar-to-electricity efficiencies (η) were measured to be 4.38% and 3.68% for the cells with PMII/CB and BMII/CB, respectively, the corresponding values without CB were 0.6% and 0.3%; indicating the remarkable role played by the carbon material in the electrolyte. When the CB was replaced with polyaniline-loaded carbon black (PACB), an efficiency of 5.81% was obtained, at 100 mW cm−2 AM1.5 illumination using PMII, the highest ever reported for a quasi solid-state DSSC made without iodine. High thermal stability up to 250 °C for each component in the composite electrolytes was confirmed by thermogravimetric analyses (TGA). At-rest durability of the DSSC with PACB was studied both at room temperature and at 70 °C and was found to be far superior to that of a cell with an organic solvent electrolyte. Electrochemical impedance spectroscopy (EIS) and dark current measurements were used to substantiate the results.