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Imidazolium iodides (Im+I−s) were synthesized with different substituents of the cation and used as electrolytes in dye-sensitized solar cells (DSSCs), and the effects of such substituents were investigated in terms of the photovoltaic performance of the cells. Synthesized iodides were verified by 1H-NMR. Among the iodides, 1,3-diethylimidazolium iodide enabled a solar energy conversion efficiency of 4.8% for its DSSC, while 1-(4-acetophenyl)-3-ethylimidazolium iodide rendered an efficiency of 3.1% for its cell. In all cases the short-circuit photocurrent ( J sc) was found to increase with decrease in size of the substituent, which was also verified to be valid in the case of a quasi-solid state DSSC. Results are explained by the electrostatic interactions between solvated Im+ and negatively charged species based on the correlation between diffusion coefficients of I− and I and J sc values. These explanations are supported by steady-state voltammetry and electrochemical impedance spectroscopy (EIS). [ABSTRACT FROM AUTHOR]

The beneficial influence of incorporation of acid-treated and rutile TiO2 (r-TiO2)-modified multi-wall carbon nanotubes (MWNTs) in TiO2 films on photocurrent–voltage characteristics of dye-sensitized solar cells (DSSCs) was studied. Two different routes were adopted for the modification of acid-treated MWNTs (a-MWNTs) with r-TiO2. The films and MWNTs were characterized by electron microscopy, energy dispersive X-ray spectroscopy, XRD and Raman spectroscopy. In the case of incorporation of a-MWNTs with r-TiO2 modification, short-circuit photocurrent ( J sc) of the pertinent DSSC increased by 35% compared with that of a cell with bare TiO2 film. The open-circuit voltage remained almost the same for all cases. The enhanced J sc is explained by the increased surface area of the film, enhanced cluster formation of TiO2 particles around a-MWNTs, and improved interconnectivity of TiO2 particles in the presence of a-MWNTs. [ABSTRACT FROM AUTHOR]