Electrochemical reversibility and fast bimolecular exchange reaction found for VO(salen) gave rise to a highly efficient redox mediation to enhance the photocurrent of a dye-sensitized solar cell, leading to an excellent photovoltaic performance with a conversion efficiency of 5.4%. A heterogeneous electron-transfer rate constant at an electrode (k0) and a second-order rate constant for an electron self-exchange reaction (k(ex)) were proposed as key parameters that dominate the charge transport property, which afforded a novel design concept for the mediators based on their kinetic aspects.

A supramolecular gelator, 2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPO)-substituted cyclohexanediamine derivative, was synthesized, and its excellent charge-transporting capability was explored. The gels with organic solvents and electrolytes, or with ionic liquids, were formed via reversible sol–gel phase transition at ca. 50 °C. The organogels displayed electrochemical redox responses at E 1/2 = 0.72 V (vs Ag/AgCl) ascribed to the TEMPO moiety. Charge diffusion coefficient of the gel reached 3.3 × 10–7 cm2/s even in the quasi-solid state, which was comparable to those of the homogeneous solution (ca. 10–6). The high charge-transporting capability led to the tremendously large current density (a diffusion limited one) of ca. 1.0 mA/cm2 on a current collector and long distance for the charge-transporting beyond the organogel thickness of 50 μm. A half-cell of the organogel performed a plateau output voltage at the E 1/2, very high rate, and almost quantitative charging–discharging, and it had cyclability without any additives such as conductive carbons and binder polymers.

Two pendant-type naphthalene diimide (NDI) polymers bearing a polynorbornene backbone were prepared and their electrochemical properties explored.

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