Dye-sensitized TiO 2 solar cells were assembled using rigid or flexible transparent electrodes (a conductive film deposited on glass or on poly(ethylene terephthalate) as substrates and a polymer electrolyte based on I 3 -/Iand poly(epichlorohydrin-co-ethylene oxide)). The cells were characterized by current-potential curves and electrochemical impedance spectroscopy under different light intensities. Under 100 mW cm -2 illumination, the rigid cell exhibited an open circuit potential V OC ) 0.82 V, a short-circuit photocurrent I SC ) 2.2 mA cm -2 , and an efficiency η ) 1%; for the flexible cell, V OC ) 0.72 V, I SC ) 0.40 mA cm -2 , and η ) 0.1%. Under illumination, impedance spectra of the cells exhibited three semicircles. In the dark, both systems presented very high impedance. The differences in the efficiency and the impedance spectra of both cells were compared and discussed.
The interface [BuMeIm][Tf2N]/electrode, where [BuMeIm][Tf2N] stands for the ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, was characterized by electrochemical impedance spectroscopy at different temperatures and for different electrode materials: platinum (Pt, metallic), glassy carbon (GC, high conductivity), carbon nitride (a-CNx, mean conductivity), and boron-doped diamond (BDD, semiconducting with a quasimetallic character). For Pt, GC, and a-CNx, the behavior of the interface could be described by the same equivalent electrical circuit. In the case of BDD, a parallel combination of Rsc and Csc was introduced into the circuit to take into account the potential drop due to the development of a space charge region within the material. The Mott-Schottky plots have confirmed the polycrystalline semiconductor character of the BDD material, and the boron concentration estimated is fully consistent with the B amount introduced for the synthesis. The variations of the double-layer capacitance as a function of potential were found to be camel shaped for all electrode materials at the highest studied temperature. This is consistent with the prediction of Kornyshev's theory as low values of the packing parameter γ were estimated by simulation (lower than 0.33). An increase of the double-layer capacitance is found with the temperature similarly to most of the results obtained for molten salts.
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