A low molecular weight amphiphilic organogelator capable of forming intermolecular hydrogen bonds and well-organized supramolecular structures was found to efficiently gel low-viscosity binary mixtures of ionic liquids at low concentrations. With this gelator it is possible to prepare stable quasi-solid-state dye-sensitized solar cells (DSCs). At a gelator concentration of only 2 wt%, the sol-gel transition temperature (T gel ) based on the lowest viscosity ionic liquid mixture was at 108 uC, well above the service temperature. Due to the thermoreversible nature of the system, the cells can be conveniently filled with a low-viscosity liquid. Upon cooling and formation of the gel a mechanically stable quasi-solid-state electrolyte was obtained. We successfully employed this quasi-solid ionic liquid electrolyte in DSCs and obtained an efficiency of 6.3% at full sunlight irradiation and maintained its stability during the light soaking accelerating stress test at 60 uC over 1000 h.
ABSTRACT:A study on the influence of the crystal modification (␣ and ) of isotactic polypropylene (i-PP) films on the resulting electret properties is presented. Two commercial nucleating agents, sodium 2,2Ј-methylene-bis(4,6-di-tertbutylphenyl)-phosphate (NA11) and N,NЈ-dicyclo-hexyl-2,6-naphthalene-dicarbox-amide (NU100), were employed in this investigation. Isothermal charge decay was measured at 90°C. In hot pressed isotropic polypropylene films, no significant differences in the charge storage properties were observed for ␣-and -nucleated specimens. In addition, the article presents the influence of the nucleating agents at different concentrations on the PP-film morphology of biaxially stretched films with respect to electret features. It was possible to prepare elongated cavities with the virtually insoluble NA11 additive during stretching, even at concentrations below 0.3 wt %. These films displayed slightly improved electret properties in comparison to stretched neat PP films due to generated cavities acting as barriers for the drift of charges. Various draw ratios were also studied for i-PP films with 0.15 wt % NA11.
A new powerful class of low-molecular-weight amphiphilic compounds has been synthesized and their structure-property relationships with respect to their gelation ability of organic solvents have been investigated. These compounds are able to gel organic solvents over a broad range of polarity. Especially polar solvents such as valeronitrile and gamma-butyrolactone can be gelled even at concentrations far below 1 wt %. It was found that the gelation ability of these asymmetrically substituted p-phenylendiamines depends on a well-balanced relation of the terminal head group, the units involved in hydrogen bonding (amide or urea groups), and on the length of the alkyl chain. With this class of new gelators it is possible to tailor thermal and mechanical properties in different organic solvents and open various application possibilities.
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