Efficient ruthenium sensitizer with an extended π-conjugated terpyridine ligand for dye-sensitized solar cells.

A ruthenium sensitizer with an extended π-conjugated terpyridine (TUS-42) has been synthesized for dye-sensitized solar cells (DSCs). Upon extension of the π-conjugated system of the terpyridine ligand, the conversion efficiency of the DSC with TUS-42 improved successfully to 10.7%, which is almost comparable to that of one of the most efficient ruthenium sensitizers (Black dye).

Novel near-infrared carboxylated 1,3-indandione sensitizers for highly efficient flexible dye-sensitized solar cells.

Three novel metal-free organic dyes (DN458, DN475 and DN484) were designed for use in plastic-substrate dye-sensitized solar cells (PDSCs). The photoelectric conversion region of DN475 was successfully expanded into the near-infrared region. As a result, an energy conversion efficiency of 5.

Ruthenium sensitizers with a hexylthiophene-modified terpyridine ligand for dye-sensitized solar cells: synthesis, photo- and electrochemical properties, and adsorption behavior to the TiO2 surface.

Two novel ruthenium sensitizers with a hexylthiophene-modified terpyridine ligand (TUS-35 and TUS-36) were synthesized to improve the molar absorptivity of the previously reported ruthenium sensitizer (TBA)[Ru{4'-(3,4-dicarboxyphenyl)-4,4″-dicarboxyterpyridine}(NCS)3], TBA = tetrabutylammonium (TUS-21). A relatively strong absorption appeared at ∼380 nm, and the molar absorption coefficient at the metal-to-ligand charge transfer (MLCT) band decreased in TUS-35 by introducing a 2-hexylthiophene unit to the 5-position of the terpyridine-derived ligand. For comparison, a relatively strong absorption was observed at ∼350 nm without decreasing the molar absorption coefficient at the MLCT band in TUS-36 by introducing a 2-hexylthiophene unit to the 4-position of the terpyridine-derived ligand.

Novel ruthenium sensitizers having different numbers of carboxyl groups for dye-sensitized solar cells: effects of the adsorption manner at the TiO₂ surface on the solar cell performance.

Two novel ruthenium sensitizers having multiple carboxyl groups ((TBA)[Ru{4'-(3,4-dicarboxyphenyl)-4,4″-dicarboxyterpyridine}(NCS)3] (TUS-21) and (TBA)[Ru{4'-(3-carboxyphenyl)-4,4″-dicarboxyterpyridine}(NCS)3] (TUS-37); TBA = tetrabutylammonium) have been synthesized as improved model sensitizers for the previously reported ruthenium sensitizer TUS-20 ((TBA)[Ru{4'-(3,4-dicarboxyphenyl)terpyridine}(NCS)3]). The absorption maxima of two MLCT bands and the absorption onsets of TUS-21 and TUS-37 were shifted to longer wavelengths of about 30 nm in comparison to those of TUS-20 by introducing a carboxyl group to the each terminal pyridine ring of the terpyridine ligand. TUS-21 and TUS-37 showed quite similar adsorption behaviors to the TiO2 surface, and this adsorption behavior was found to be different from that of TUS-20.

Ruthenium sensitizers having an ortho-dicarboxyl group as an anchoring unit for dye-sensitized solar cells: synthesis, photo- and electrochemical properties, and adsorption behavior to the TiO₂ surface.

A novel ruthenium sensitizer ((TBA)[Ru(3',4'-dicarboxyterpyridine)(NCS)3], TBA = tetrabutylammonium, TUS-28) has been synthesized as an improved model sensitizer for (TBA)[Ru(4'-(3,4-dicarboxyphenyl)terpyridine)(NCS)3] (TUS-20). The molar absorptivity of TUS-28 in the whole visible region was smaller than that of TUS-20 due to the absence of the phenyl ring at the terpyridine ligand. On the other hand, the energy levels of HOMO and LUMO of TUS-28 were still suitable for effective electron transfer reactions in dye-sensitized solar cells (DSCs).

A new cosensitization method using the Lewis acid sites of a TiO₂ photoelectrode for dye-sensitized solar cells.

Co-sensitized dye-sensitized solar cells using black dye and a pyridine-anchor dye (NI5 or YNI-2) showing site-selective adsorption behaviour at the TiO2 surface have been prepared for the first time to reduce the competitive adsorption between the two dyes.

Novel ruthenium sensitizers with a dianionic tridentate ligand for dye-sensitized solar cells: the relationship between the solar cell performances and the electron-withdrawing ability of substituents on the ligand.

Five novel ruthenium sensitizers (TUS sensitizers) with a dianionic tridentate ligand (pyridine-2,6-dicarboxyamidato and its derivatives) have been synthesized for application to dye-sensitized solar cells (DSCs). These TUS sensitizers have much larger molar absorption coefficients in the wavelength range below 600 nm compared with those of Black dye which is a structural analog and a highly efficient ruthenium sensitizer. The energy levels of HOMOs and LUMOs of TUS sensitizers shifted to the positive direction with increasing the electron-withdrawing ability of the substituents on the dianionic tridentate ligand.

Dependence of the efficiency improvement of black-dye-based dye-sensitized solar cells on alkyl chain length of quaternary ammonium cations in electrolyte solutions.

Dependence of the suppression of the backward electron transfer reaction from the TiO2 photoelectrode to I3(-) in the electrolyte on the alkyl chain length of the quaternary ammonium cation has been investigated for further efficiency improvement of high-performance cosensitized dye-sensitized solar cells (DSCs). The tetraheptylammonium cation was found to be more effective than the tetraethylammonium and tetrabutylammonium cations for the suppression of the backward electron transfer reaction without changing the conduction band energy of TiO2. 12.

Characterization of photovoltaic performance of the dye-sensitized solar cell with a novel ruthenium complex having a bisdemethoxycurcumin as a ligand.

The first example of a ruthenium sensitizer (TUS-22) having a natural dye, bisdemethoxycurcumin, as a ligand has been synthesized. The dye-sensitized solar cell based on this novel dye showed 5.8% conversion efficiency under AM 1.

Effective enhancement of the performance of black dye based dye-sensitized solar cells by metal oxide surface modification of the TiO2 photoelectrode.

Effective enhancement of the performance of black dye based dye-sensitized solar cells has been achieved by MgO or Al(2)O(3) surface modification of the TiO(2) photoelectrode. The conversion efficiency was improved from 10.4% to 10.

Effects of dye-adsorption solvent on the performances of the dye-sensitized solar cells based on black dye.

The effects of the dye-adsorption solvent on the performances of the dye-sensitized solar cells (DSSCs) based on black dye have been investigated. The highest conversion efficiency (10.6 %) was obtained in the cases for which 1-PrOH and the mixed solvent of EtOH and tBuOH (3:1 v/v) were employed as dye-adsorption solvents.

Synthesis of novel beta-diketonate bis(bipyridyl) Os(II) dyes for utilization of infrared light in dye-sensitized solar cells.

Bis(bipyridyl) osmium(II) dyes having a beta-diketonate ligand were synthesized in order to utilize visible and infrared light for dye-sensitized solar cells. Compared to black dye, under AM 1.5 irradiation (100 mW cm(-2)), DSCs using our novel Os dyes exhibited a better spectral response in the near-IR region (by 1050 nm) and showed a higher J(SC) value of 23.

Highly efficient plastic substrate dye-sensitized solar cells using a compression method for preparation of TiO(2) photoelectrodes.

The efficiency of a plastic-substrate dye-sensitized solar cell was much improved by a new method consisting of a press method without heat treatment, light confinement effect of TiO(2) film and water-based TiO(2) paste; this device shows the highest light-to-electrical energy conversion efficiency based on plastic-substrate dye-sensitized solar cells, 7.4% under 100 mW cm(-2) (1 sun) AM1.5 illumination.

Lithium ion effect on electron injection from a photoexcited coumarin derivative into a TiO2 nanocrystalline film investigated by visible-to-IR ultrafast spectroscopy.

The dynamics of ultrafast electron injection from a coumarin derivative (NKX-2311), which is an efficient photosensitizer for dye-sensitized solar cells, into the conduction band of TiO(2) nanocrystalline films have been investigated by means of femtosecond transient absorption spectroscopy in a wide wavelength range from 600 nm to 10 mum. In the absence of Li(+) ions, electron injection into the TiO(2) conduction band occurred in about 300 fs. In the presence of Li(+) ions, however, electron injection occurred within approximately 100 fs, and the oxidized dye generated was found to interact with nearby Li(+) ions.

Photophysical and (photo)electrochemical properties of a coumarin dye.

A new coumarin dye, cyano-{5,5-dimethyl-3-[2-(1,1,6,6-tetramethyl-10-oxo-2,3,5,6-tetrahydro-1H,4H,10H-11-oxa-3a-aza-benzo[de]anthracen-9-yl)vinyl]cyclohex-2-enylidene}-acetic acid (NKX-2753), was prepared and characterized with respect to photophysical and electrochemical properties. It was employed as a dye sensitizer in dye-sensitized solar cells and showed efficient photon-to-electron conversion properties. The photocurrent action spectrum exhibited a broad feature with a maximum incident photon-to-electron conversion efficiency (IPCE) of 84% at 540 nm, which is comparable to that for the famous red dye RuL2(NCS)2 (known as N3), where L stands for 2,2'-bipyridyl-4,4'-dicarboxylic acid.

Synthesis of tubular titanate via a self-assembly and self-removal process.

Novel morphology titanate tubes were successfully synthesized via a self-assembly and self-removal process. After the product was treated by calcinating and washing, crystalline TiO2 tubes were obtained. In this study, two new concepts are applied to design the synthetic route: (i) titanium glycolate rods obtained from an ethylene glycol-mediated process and titanate sheets synthesized using the hydrothermal process were used as the template and the precursor, respectively, and ii) the template was directly removed in the reaction without posttreatment.

Significant efficiency improvement of the black dye-sensitized solar cell through protonation of TiO2 films.

This paper describes the influence of acid pretreatment ofTiO2 mesoporous films prior to dye sensitization on the performance of dye-sensitized solar cells based on [(C4H9)4N]3[Ru(Htcterpy)(NCS)3] (tcterpy = 4,4',4"-tricarboxy- 2,2',2"-terpyridine), the so-called black dye. The HCl pretreatment caused an increase in overall efficiency by 8%, with a major contribution from photocurrent improvement. It is speculated, from the analysis of incident photon-to-electron conversion efficiency, UV-vis absorption spectra, redox properties of the dye and TiO2, and the impedance spectra of the dye-sensitized solar cells, that photocurrent enhancement is attributed to the increases in electron injection and/or charge collection efficiency besides the improvement of light harvesting efficiency upon HCl pretreatment.

Effect of additives on the photovoltaic performance of coumarin-dye-sensitized nanocrystalline TiO2 solar cells.

The effects of deoxycholic acid (DCA) and 4-tert-butylpyridine (TBP) as additives on the photovoltaic performance of coumarin-dye-sensitized nanocrystalline TiO2 solar cells were investigated. DCA coadsorption improved both the photocurrent and photovoltage of the solar cells, even though it decreased the amount of dye adsorbed on the TiO2 electrode. The improved photocurrent may arise from suppression of the deactivation of the excited state via quenching processes between dye molecules or a more negative LUMO level of the dye in the presence of DCA, resulting in a high electron-injection yield from the dye into TiO2.

Synthesis of single-crystal manganese dioxide nanowires by a soft chemical process.

α- and β-MnO(2) single-crystal nanowires have been successfully synthesized through a soft chemical process, which involves no catalysts or templates. The diameters of the nanowires are about 10-40 nm and the lengths up to several tens of micrometres. Experimental results showed that MnO(2) polymorphic forms can be synthesized by selected-control reaction temperatures and their crystal phases in the nanowires were confirmed by XRD and TEM measurement.

Photoelectrochemical decomposition of water on nanocrystalline BiVO4 film electrodes under visible light.

The nanocrystalline BiVO4 film electrode on conducting glass showed an excellent efficiency (IPCE = 29% at 420 nm) for the decomposition of water under visible light.

Panchromatic sensitization of nanocrystalline TiO2 with cis-Bis(4-carboxy-2-[2'-(4'-carboxypyridyl)]quinoline)bis(thiocyanato-N)ruthenium(II).

We compared the spectral (IR and Raman), electrochemical, and photoelectrochemical properties of nanocrystalline TiO(2) sensitized with the newly synthesized complex [NBu(4)](2)[cis-Ru(Hdcpq)(2)(NCS)(2)] (1; [NBu(4)](+) = tetrabutylammonium cation; H(2)dcpq = 4-carboxy-2-[2'-(4'-carboxypyridyl)]quinoline) with those of TiO(2) sensitized with [NBu(4)](2)[cis-Ru(Hdcbpy)(2)(NCS)(2)] (2; H(2)dcbpy = 4,4'-dicarboxy-2,2'-bipyridine) and [NBu(4)](2)[cis-Ru(Hdcbiq)(2)(NCS)(2)] (3; H(2)dcbiq = 4,4'-dicarboxy-2,2'-biquinoline). Complex 1 achieved efficient sensitization of nanocrystalline TiO(2) films over a wide visible and near-IR region, generating a large short-circuit photocurrent. The absorbed photon-to-current conversion efficiency decreased in the order 2 > 1 > 3 with the decrease in the free energy change (-Delta G(inj)) of the electron injection from the ruthenium complex to TiO(2).

Novel polyene dyes for highly efficient dye-sensitized solar cells.

We have developed an efficient and novel polyene-dye-sensitized nanocrystalline TiO2 solar cells producing a 6.8% solar energy-to-electricity conversion efficiency (eta) under AM 1.5 irradiation (100 mW cm(-2)): short-circuit current density (Jsc), 12.