We proposed a simple yet robust film treatment method with methanol having only one hydroxyl group to enhance the conductivity of poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) by four orders of magnitude. Different methods of film treatment: immersing PEDOT:PSS film in the methanol solution; dropping methanol on the film; and a combination of these are employed and the results are compared. The conductivity of PEDOT:PSS films was enhanced from 0.3 S cm À1 to 1362 S cm À1 after film treatment with methanol. Other alcohols like ethanol and propanol were also used to treat the PEDOT:PSS film and showed inferior conductivity enhancement compared to methanol. The conductivity enhancement was greatly affected by the hydrophilicity and dielectric constant of the alcohols used. The mechanism of conductivity enhancement was investigated through various characterization techniques including FTIR, XPS and AFM. Removal of the insulator PSS from the film, and morphology and conformational changes are the mechanisms for the conductivity enhancement. The treated films also showed high transmittance and low sheet resistance desirable for a standalone electrode. ITO-free polymer solar cells were fabricated using PEDOT:PSS electrodes treated with methanol and showed almost equal performance to ITO electrodes.

One-dimensional cobalt sulfide (CoS) acicular nanorod arrays (ANRAs) were obtained on a fluorine-doped tin oxide (FTO) substrate by a two-step approach. First, Co(3)O(4) ANRAs were synthesized, and then they were converted to CoS ANRAs for various periods. The compositions of the films obtained after various conversion periods were verified by X-ray diffraction, UV-visible spectrophotometry, and X-ray photoelectron spectroscopy; their morphologies were examined at different periods by scanning electron microscopic and transmission electron microscopic images. Electrocatalytic abilities of the films toward I(-)/I(3)(-) were verified through cyclic voltammetry (CV) and Tafel polarization curves. Long-term stability of the films in I(-)/I(3)(-) electrolyte was studied by CV. The FTO substrates with CoS ANRAs were used as the counter electrodes for dye-sensitized solar cells; a maximum power conversion efficiency of 7.67% was achieved for a cell with CoS ANRAs, under 100 mW/cm(2), which is nearly the same as that of a cell with a sputtered Pt counter electrode (7.70%). Electrochemical impedance spectroscopy was used to substantiate the photovoltaic parameters.

A dye-sensitized solar cell (DSSC) using Ru complexes as a photosensitizer was first reported by ORegan and Grätzel in 1991.[1] The low-cost, easy preparation make DSSC one of the most promising photovoltaic cells for conversion of sunlight to electricity. Numerous sensitizers have been prepared, and their performance has been tested. [2][3][4][5][6][7][8][9][10] A conversion efficiency of up to 11 % was achieved by using cis-di(thiocyanato)bis(2,2'-bipyridyl-4,4'-dicarboxylate)ruthenium(II) (N3) as a photosensitizer. [11][12] However, the conversion efficiency of DSSCs is still lower than that of the silicon-based photovoltaic cells. To obtain a high conversion efficiency, optimization of the short-circuit photocurrent (I sc ) and open-circuit potential (V oc ) of the cell is essential. The value of V oc depends on the edge of conduction band in TiO 2 and the redox potential of I À / I 3 À , otherwise I sc is related to the interaction between TiO 2 and the sensitizer as well as the absorption coefficient of the sensitizer. The conduction band of TiO 2 was known to have a Nernstian dependence on pH. [13][14] Thus, the molecular engineering of the ruthenium complexes for achieving the highest efficiency was attempted to increase the molar absorption coefficient and reduce the number of protons on the complexes. 4,4'-Dicarboxylic acid-2,2'-bipyridine (dcbpy) has been considered as the best anchoring ligand in Ru sensitizers.[15] Finding new metal-complex sensitizers with higher conversion efficiency was achieved by modifying one of the anchoring ligands. Replacement of one of the dcbpy anchoring ligands with a highly conjugated ancillary ligand represents a molecular engineering approach for increasing the absorption coefficient and therefore the photocurrent density of the sensitizers as reported by Grätzel and coworkers. [16][17][18][19][20] Herein, we report a new ruthenium photosensitizer CYC-B1 in which one of the dcbpy ligands in N3 was replaced with abtpy, a bipyridine ligand substituted with alkyl bithiophene groups. CYC-B1 has the highest absorption coefficient among the Ru-based photosensitizers used in DSSCs, and its power-conversion efficiency is 10 % higher than that of N3 under the same cell fabrication and measuring procedures carried out in our laboratory.CYC-B1 was prepared in a typical one-pot synthesis, [20] and its structure (Scheme 1) was identified from NMR spectroscopy, mass spectrometry, and elemental analysis. The electronic absorption spectra of the free dcbpy and abtpy ligands, CYC-B1, and N3 in DMF are displayed in Figure 1, and the optical data are summarized in Table 1. The absorption maximum (l max ) assigned to the p-p* transition for dcbpy and abtpy are 299 nm and 375 nm, respectively. The absorption maximum of abtpy is red-shifted by 76 nm, which is attributed to its longer conjugation length, compared to that of dcbpy. The absorption spectrum of CYC-B1 shows three bands centered at 553 nm, 400 nm, and 312 nm. Based on comparison with the free abtpy ligand and the homoleptic compl...

This review describes recent developments relating to the synthesis of viologen-based electrochromes with co-redox species and their ECD performance.

The capacitance mechanisms of magnetite ͑Fe 3 O 4 ͒ electrochemical capacitor in Na 2 SO 3 , Na 2 SO 4 , and KOH aqueous solutions have been investigated by electrochemical quartz-crystal microbalance analysis, along with cyclic voltammetry and X-ray photoelectron spectroscopy. The oxide thin-film electrode was prepared by an electroplating method, and exhibits a capacitance of ϳ170, 25, and 3 F/g in 1.0 M Na 2 SO 3 ͑aq͒, Na 2 SO 4 ͑aq͒, and KOH͑aq͒, respectively. Strong specific adsorption of the anion species was evidenced in all solutions. Experimental results indicate that, in Na 2 SO 3 ͑aq͒, the capacitive current of magnetite electrode originates from the combination of electric double-layer capacitance ͑EDLC͒ and the pseudocapacitance that involves successive reduction of the specifically adsorbed sulfite anions, from SO 3 2− through, e.g., S 2− , and vice versa. In Na 2 SO 4 ͑aq͒, the current is due entirely to EDLC. Furthermore, due to the specific adsorption behavior, magnetite exhibits high EDLC, Ͼ30 F/cm 2 , in both Na 2 SO 3 and Na 2 SO 4 solutions. The lowest capacitance of magnetite was observed in KOH, which is attributed to the formation of an insulating layer on the magnetite surface.Electrical double-layer capacitance ͑EDLC͒ arises from the potential dependence of the surface density of charges stored electrostatically ͑i.e., nonfaradaically͒ at the interfaces of capacitor electrodes. 1-4 EDLC electrochemical capacitors are complemented by capacitors based on the so-called pseudocapacitance, which involves faradaic reactions but behaves like a capacitor rather than a galvanic cell. [5][6][7][8][9][10][11][12][13][14][15] While EDLC typically has a specific capacitance in the order of 10 F/cm 2 of true surface area of the electrode material, pseudocapacitance often has a value that is 10 to 100 times greater.The most widely studied pseudocapacitive material is hydrous RuO 2 . 5-9 The pseudocapacitance of this material is known to arise from successive multielectron transfer at Ru cation sites, from, e.g., Ru 2+ to Ru 3+ and then to Ru 4+ , balanced by conversion of the OH − site to the O 2− sites in the oxide structure by proton transfer. There is a continuously variable degree of oxidation/reduction, leading to the capacitor behavior. Because RuO 2 is very expensive, searching for cheaper pseudocapacitive electrode materials has been a major subject in the research on electrochemical capacitors. Goodenough et al. 10,11 reported in 1999 the observation of pseudocapacitance on hydrous MnO 2 . Its mechanism was suggested to involve multielectron transfer at Mn cation sites, balanced by intercalation/extraction of cations within the oxide structure.An aqueous Fe 3 O 4 ͑magnetite͒ electrochemical capacitor is another emerging inexpensive system. 12-16 Large capacitances have been reported in alkali sulfites and sulfate solutions. In particular, the capacitance of the oxide was found to be sensitive to the anion species but not to either alkaline cations or electrolyte pH ͑ഛ11͒. These behaviors sugge...