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Coordinatively induced length control of W18O49 nanorods are developed using thermal decomposition of W(CO)(sub 6) in octyl ether solutions of single or mixed capping agents, oleic acid (OA), oleic acid/hexadecylamine (HDA), and oleic acid/trioctylphosphine oxide (TOPO). The strong coordinating power and steric bulkiness of TOPO interrupts the growth of the nanorods, the rearrangement of the end face atoms, and the fusion of the lateral faces, which thereby increases the oxygen defects and the photoluminescence intensity.

Ti[O.sub.2] thin films were prepared on electrochemically etched porous Si by anodic oxidative hydrolysis of Ti[Cl.sub.3] for the purpose of solar cell application. We compared electrochemical and photoelectrochemical properties of the Ti[O.sub.2]-deposited porous Si electrodes (Ti[O.sub.2]/porous Si) with those of a porous Si electrode. The Ti[O.sub.2]/porous Si showed prolonged stability of photoluminescence and enhancements of photovoltage and photocurrent by 0.13 V and 67% increase, respectively, in comparison with porous Si due to the reduction of surface traps for charge carriers in the presence of Ti[O.sub.2] thin layer. [Li.sup.+] and [Na.sup.+] ions exhibited intercalation and deintercalation through the electrodeposited Ti[O.sub.2] film.

The cation transport characteristics of Prussian blue (PB) and PB + cetyltrimethylammonium bromide (CTAB) electrodes for [K.sup.+], [Na.sup.+], [Li.sup.+], and N[H.sub.4.sup.+] ions are analyzed. The symmetric redox peaks for a PB + CTAB films has represented an ideal cyclic voltammetric (CV) pattern for a PB-modified electrode.

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]

A Prussian blue (PB) film was deposited on a glassy carbon (GC) electrode by cyclic voltammetry in the presence of the cationic surfactant cetyltrimethylammonium bromide (CTAB). The electrode thus formed showed 4-fold enhancements in redox current and charge values in pure KCl electrolyte as well as greater stability than an electrode prepared in the absence of CTAB. This improved performance of a PB CTAB electrode versus a PB electrode was further demonstrated using SEM, XRD, and electrochemical impedance spectroscopy (EIS) measurements. A comparative study was undertaken on the cation transport characteristics of PB and PB CTAB electrodes for Na, Li, and NH4ions. We obtained a CV pattern for a CTAB-promoted PB film, which showed ideal Nernstian behavior at all scan rates from 5 to 140 mV s-1. Conditions for the formation and preservation of these ideal and stable PB films are discussed. Possible mechanisms for the beneficial effects of CTAB are proposed. [ABSTRACT FROM AUTHOR]

In this study, a Ru(ii) dye was linked to another TiO2-attached Ru(ii) dye through the linker, trans-1,2-bis(4-pyridyl)ethylene (tbpe), and such TiO2 film electrodes were used in dye-sensitized solar cells (DSSCs). The mononuclear Ru(ii) dyes selected were N3 ([Ru(dcbpyH2)2(NCS)2], dcbpyH2= 2,2′-bipyridyl-4,4′-dicarboxylic acid), N719 ([(C4H9)4N]2[Ru(dcbpyH)2(NCS)2]), and N749 ([(C4H9)4N]3[Ru(tcterpy)(NCS)3]·3H2O, tcterpy = 4,4′,4″-tricarboxy-2,2′:6′,2″-terpyridine). The photovoltaic characteristics of the DSSCs prepared using the above-mentioned TiO2 film electrodes were examined. The DSSC with the dinuclear dye, N719-tbpe-N719 had the highest short-circuit photocurrent density (Jsc) and thereby the highest conversion efficiency compared with the other cells sensitized by the other mononuclear or dinuclear Ru(ii) dyes. The Jsc enhancement was attributed to an increase in the conduction band electrons of TiO2 due to the efficient intramolecular charge and energy transfer from the linked dye molecule to the immobilized molecule through a chain of conjugated double bonds in tbpe. These transfers are explained based on the relative LUMO levels of the dyes. [ABSTRACT FROM AUTHOR]

Titanium dioxide (TiO2) film for dye-sensitized solar cells (DSSCs) has surface defects such as oxygen vacancies created during the annealing process. The authors used a plasma treatment technique to reduce defects on TiO2 surfaces. They investigated the influence of different gas plasma treatments of TiO2 film on the photoelectric performance of DSSC. Short-circuit photocurrent density (Jsc), open-circuit photovoltage (Voc), and the amount of adsorbed dye for DSSCs were measured. As a result, the solar-to-electricity conversion efficiencies of the O2- and N2-treated cells increased by 15%–20% compared to untreated cells. On the other hand, solar energy conversion efficiency of CF4-plasma treated cells decreased drastically. The increased amount of adsorbed dye on the TiO2 film was measured by time-of-flight secondary ion mass spectrometry. TiO2 surfaces modified by plasma treatment were characterized using analytical instruments such as x-ray photoelectron spectroscopy and near-edge x-ray absorption fine structure. [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]

The effects of metallic supporting substrates in nanocrystalline TiO2 working electrodes of dye-sensitized solar cells on photocurrent-voltage (J-V) characteristics were investigated. For W, Ti, stainless steel, and Zn that can produce semiconductor oxides during annealing, the short-circuit photocurrent density (Jsc) is related to the conduction band energy levels of the metal oxides. The metals that produce insulating oxides, Al, Co, and Ni, were found to be also useful supporting substrates when both thin layers of ITO and SiOx were sputtered on the metal surfaces. [ABSTRACT FROM AUTHOR]