DFT-INDO/S modeling of new high molar extinction coefficient charge-transfer sensitizers for solar cell applications

A new ruthenium(II) complex, tetrabutylammonium [ruthenium (4-carboxylic acid-4'-carboxylate-2,2'-bipyridine)(4,4'-di(2-(3,6-dimethoxyphenyl)ethenyl)-2,2'-bipyridine)(NCS)(2)] (N945H), was synthesized and characterized by analytical, spectroscopic, and electrochemical techniques. The absorption spectrum of the N945H sensitizer is dominated by metal-to-ligand charge-transfer (MLCT) transitions in the visible region, with the lowest allowed MLCT bands appearing at 25 380 and 18 180 cm(-1). The molar extinction coefficients of these bands are 34 500 and 18 900 M(-1) cm(-1), respectively, and are significantly higher when compared to than those of the standard sensitizer cis-dithiocyanatobis(4,4'-dicarboxylic acid-2,2'-bipyridine)ruthenium(II). An INDO/S and density functional theory study of the electronic and optical properties of N945H and of N945 adsorbed on TiO(2) was performed. The calculations point out that the top three frontier-filled orbitals have essentially ruthenium 4d (t(2g) in the octahedral group) character with sizable contribution coming from the NCS ligand orbitals. Most critically the calculations reveal that, in the TiO(2)-bound N945 sensitizer, excitation directs charge into the carboxylbipyridine ligand bound to the TiO(2) surface. The photovoltaic data of the N945 sensitizer using an electrolyte containing 0.60 M butylmethylimidazolium iodide, 0.03 M I(2), 0.10 M guanidinium thiocyanate, and 0.50 M tert-butylpyridine in a mixture of acetonitrile and valeronitrile (volume ratio = 85:15) exhibited a short-circuit photocurrent density of 16.50 +/- 0.2 mA cm(-2), an open-circuit voltage of 790 +/- 30 mV, and a fill factor of 0.72 +/- 0.03, corresponding to an overall conversion efficiency of 9.6% under standard AM (air mass) 1.5 sunlight, and demonstrated a stable performance under light and heat soaking at 80 degrees C.     

Spectroelectrochemical studies of hole percolation on functionalised nanocrystalline TiO2 films: a comparison of two different ruthenium complexes

We report the application of spectroelectrochemical techniques to compare the hole percolation dynamics of molecular networks of two ruthenium bipyridyl complexes adsorbed onto mesoporous, nanocrystalline TiO(2) films. The percolation dynamics of the ruthenium complex cis-di(thiocyanato)(2,2'-bipyridyl-4,4'-dicarboxylic acid)-(2,2'-bipyridyl-4,4'-tridecyl) ruthenium(II), N621, is compared with those observed for an analogous dye with an additional tri-phenyl amine (TPA) donor moiety, cis-di(thiocyanato)(2,2'-bipyridyl-4,4'-dicarboxylic acid)-(2,2'-bipyridyl-4,4'-bis(vinyltriphenylamine)) ruthenium(II), HW456. The in situ oxidation of these ruthenium complexes adsorbed to the TiO(2) films is monitored by cyclic voltammetry and voltabsorptometry, whilst the dynamics of hole (cation) percolation between adsorbed ruthenium complexes is monitored by potentiometric spectroelectrochemistry and chronoabsorptometry. The hole diffusion coefficient, D(eff), is shown to be dependent on the dye loading on the nanocrystalline TiO(2) film, with a threshold observed at ～60% monolayer surface coverage for both dyes. The hole diffusion coefficient of HW456 is estimated to be 2.6 × 10(-8) cm(2)/s, 20-fold higher than that obtained for the control N621, attributed to stronger electronic coupling between the TPA moieties of HW456 accelerating the hole percolation dynamics. The presence of mercuric ions, previously shown to bind to the thiocyanates of analogous ruthenium complexes, resulted in a quenching of the hole percolation for N621/TiO(2) films and an enhancement for HW456/TiO(2) films. These results strongly suggest that the hole percolation pathway is along the overlapped neighbouring -NCS groups for the N621 molecules, whereas in HW456 molecules cation percolation proceeds between intermolecular TPA ligands. These results are discussed in the context of their relevance to the process of dye regeneration in dye sensitised solar cells, and to the molecular wiring of wide bandgap inorganic materials for battery and sensing applications.     

Visible-light-sensitized production of hydrogen using perfluorosulfonate polymer-coated TiO2 nanoparticles: an alternative approach to sensitizer anchoring

TiO(2) sensitized by derivatized ruthenium bipyridyl complexes has been intensively investigated as a tool to utilize visible light. This article describes an alternative approach to attaching ruthenium complex sensitizers at the TiO(2)/H(2)O interface, which is a much simpler and more efficient way to produce hydrogen. The surface of TiO(2) particles are simply coated with perfluorosulfonate polymer (cation-exchange resin: Nafion), and then Ru(bpy)(3)(2+) (as a cationic form), whose bipyridyl ligands are not functionalized with carboxylic acid groups, are bound within the Nafion layer through electrostatic attraction. The visible-light-induced production of H(2) on Nf/TiO(2) using simple Ru(bpy)(3)(2+) as a sensitizer is far more efficient than that on Ru(dcbpy)(3)-TiO(2), upon which many sensitized photoelectrochemical conversion systems are based. Effects of various experimental parameters such as pH, concentration of Ru(bpy)(3)(2+), Nafion loading, and the kind of TiO(2) were investigated. Under optimized conditions, the H(2) production rate was about 80 mumol/h, which corresponds to an apparent photonic efficiency of 2.6%. The roles of the Nafion layer on TiO(2) in the sensitized H(2) production are proposed to be twofold: to provide binding sites for cationic sensitizers and to enhance the local activity of protons in the surface region.     

Scanning tunneling microscopy study of black dye and deoxycholic acid adsorbed on a rutile TiO2(110)

Trithiocyanato(4,4',4'-tricarboxy-2,2':6',2'-terpyridine)ruthenium(II), "black dye", was adsorbed on a rutile TiO(2)(110) surface and imaged by an ultrahigh vacuum scanning tunneling microscope. The TiO(2)(110)-(1 x 1) surface was prepared in a vacuum, covered with pivalate monolayer, and immersed in acetonitrile containing black dye. Black dyes exchanging preadsorbed pivalates were observed on the surface as protrusions with lateral dimensions from 2 to 10 nm. Protrusions with a minimum lateral dimension of 2 nm were assigned to single, isolated black dyes, and larger protrusions were attributed to aggregated dyes. When deoxycholic acid was added to the dye solution, the number ratio of the single dyes to the aggregated dyes increased, while adsorbed deoxycholic acid was not observed.     

TiO2-CeO2介孔复合氧化物的合成及应用

以氯化十六烷基吡啶(C16PyCl)为模板剂, 在室温、中性条件下合成了TiO2-CeO2介孔复合氧化物, 分别用红外光谱(FT-IR)、X射线粉末衍射(XRD)和BET 比表面测定等技术对介孔TiO2的结构、晶相和比表面积进行了表征. 结果表明, Ce4+的引入能稳定介孔结构. 负载活性组分Ru 后, Ru 颗粒与介孔复合载体发生相互作用, 尽管可能会部分堵塞孔道, 但对于甲醇分解为CO 和H2, Ru/m-TiO2-CeO2的催化活性依然远高于Ru/m-TiO2. Ru 和CeO2之间的相互作用对甲醇分解反应表现出协同效应.     

Synthesis and characterization of dinuclear ruthenium complexes covalently linked to Ru(II) tris-bipyridine: an approach to mimics of the donor side of photosystem II

To mimic the electron-donor side of photosystem II (PSII), three trinuclear ruthenium complexes (2, 2a, 2b) were synthesized. In these complexes, a mixed-valent dinuclear Ru2(II,III) moiety with one phenoxy and two acetato bridges is covalently linked to a Ru(II) tris-bipyridine photosensitizer. The properties and photoinduced electron/energy transfer of these complexes were studied. The results show that the Ru2(II,III) moieties in the complexes readily undergo reversible one-electron reduction and one-electron oxidation to give the Ru2(II,III) and Ru2(III,III) states, respectively. This could allow for photooxidation of the sensitizer part with an external acceptor and subsequent electron transfer from the dinuclear ruthenium moiety to regenerate the sensitizer. However, all trinuclear ruthenium complexes have a very short excited-state lifetime, in the range of a few nanoseconds to less than 100 ps. Studies by femtosecond time-resolved techniques suggest that a mixture of intramolecular energy and electron transfer between the dinuclear ruthenium moiety and the excited [Ru(bpy)3]2+ photosensitizer is responsible for the short lifetimes. This problem is overcome by anchoring the complexes with ester- or carboxyl-substituted bipyridine ligands (2a, 2b) to nanocrystalline TiO2, and the desired electron transfer from the excited state of the [Ru(bpy)3]2+ moiety to the conduction band of TiO2 followed by intramolecular electron transfer from the dinuclear Ru2(II,III) moiety to photogenerated Ru(III) was observed. The resulting long-lived Ru2(III,III) state decays on the millisecond timescale.     

A swift dye uptake procedure for dye sensitized solar cells

Solar cells based on swift self-assembled sensitizer bis(tetrabutylammonium)-cis-di(thiocyanato)-N,N'-bis(4-carboxylato-4'-carboxylic acid-2,2'-bipyridine)ruthenium(II) (N719) on double layers of 12 + 4 microm thick nanocrystalline TiO2 films exhibit the incident monochromatic photon-to-current conversion efficiency (IPCE) 90% and show a short circuit current density of 17 mA cm(-2), 750 mV open circuit potential and 0.72 fill factor yielding power conversion efficiencies over 9.18% under AM 1.5 sun. For the first time highest power conversion efficiencies are obtained for dye sensitized solar cells using a swift self-assembled procedure.     

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). The open-circuit photovoltages (V(oc)'s) of dye-sensitized solar cells decreased in the order 2 > 1 > 3 with the increase in the dark current resulting from reverse electron transfer from TiO(2) to I(3)(-). The sensitizer-dependent V(oc) value can be interpreted as a result of reverse electron transfer through the sensitizing dye molecules.     

Efficient charge separation in TiO2 films sensitized with ruthenium(II)-polypyridyl complexes: hole stabilization by ligand-localized charge-transfer states

We have studied the interfacial electron-transfer dynamics on TiO(2) film sensitized with synthesized ruthenium(II)-polypyridyl complexes--[Ru(II)(bpy)(2)(L(1))] (1) and [Ru(II)(bpy)(L(1))(L(2))] (2), in which bpy=2,2'-bipyridyl, L(1)=4-[2-(4'-methyl-2,2'-bipyridinyl-4-yl)vinyl]benzene-1,2-diol, and L(2)=4-(N,N-dimethylaminophenyl)-2,2'-bipyridine-by using femtosecond transient absorption spectroscopy. The presence of electron-donor L(2) and electron-acceptor L(1) ligands in complex 2 introduces lower energetic ligand-to-ligand charge-transfer (LLCT) excited states in addition to metal-to-ligand (ML) CT manifolds of complex 2. On photoexcitation, a pulse-width-limited (<100 fs) electron injection from populating LLCT and MLCT states are observed on account of strong catecholate binding on the TiO(2) surface. The hole is transferred directly or stepwise to the electron-donor ligand (L(2)) as a consequence of electron injection from LLCT and MLCT states, respectively. This results an increased spatial charge separation between the hole residing at the electron-donor (L(2)) ligand and the electron injected in TiO(2) nanoparticles (NPs). Thus, we observed a significant slow back-electron-transfer (BET) process in the 2/TiO(2) system relative to the 1/TiO(2) system. Our results suggest that Ru(II) -polypyridyl complexes comprising LLCT states can be a better photosensitizer for improved electron injection yield and slow BET processes in comparison with Ru(II)-polypyridyl complexes comprising MLCT states only.     

Nanoparticles of amorphous ruthenium sulfide easily obtainable from a TiO2-supported hexanuclear cluster complex [Ru6C(CO)16]2-: a highly active catalyst for the reduction of SO2 with H2

TiO(2)-supported ruthenium-metal particles were derived from an anionic hexanuclear carbido carbonyl cluster [Ru(6)C(CO)(16)](2-) and compared with those prepared conventionally by impregnation of TiO(2) with a solution of RuCl(3) followed by reduction with H(2). The average sizes of the metal particles in both systems are similar, that is, 12 A for molecular cluster-derived particles and 15 A for those derived from the RuCl(3) precursor, although the size distribution is sharper in the former case. These supported particles efficiently promote the reduction of SO(2) with H(2) to give elemental sulfur. Their active form is ruthenium sulfide as confirmed by EXAFS and X-ray diffraction measurements. The nanoscale ruthenium sulfide particles, which originated from the cluster complex, have an amorphous character and show activity even at low temperature (463 K), whereas ruthenium sulfide formed from RuCl(3)-derived metal dispersion is a pyrite-type RuS(2) crystallite and needs a temperature above 513 K to effect the same catalysis. Amorphous ruthenium sulfide maintains its nano-sized scale (approximately 14 A) regardless of the reaction temperature, while RuS(2) crystallite aggregates to form larger nonuniform particles.     

Amphiphilic ruthenium sensitizers and their applications in dye-sensitized solar cells

Amphiphilic ligands 4,4'-bis(1-adamantyl-aminocarbonyl)-2,2'-bipyridine (L(1)), 4,4'-bis[5-[N-[2-(3beta-cholest-5-en-3-ylcarbamate-N-yl)ethyl]aminocarbonyl]]-2,2'-bipyridine (L(2)), 4,4'-bis[5-[N-[2-(3beta-cholest-5-en-3-ylcarbamate-N-yl)propyl]aminocarbonyl]]-2,2'-bipyridine (L(3)), and 4,4'-bis(dodecan-12-ol)-2,2'-bipyridine (L(4)) and their heteroleptic ruthenium(II) complexes of the type [Ru(II)LL(1)(NCS)(2)] (5), [Ru(II)LL(2)(NCS)(2)] (6), [Ru(II)LL(3)(NCS)(2)] (7), and [Ru(II)LL(4)(NCS)(2)] (8) (where L = 4,4'-bis(carboxylic acid)-2,2'-bipyridine) have been synthesized starting from dichloro(p-cymene)ruthenium(II) dimer. All the ligands and the complexes were characterized by analytical, spectroscopic, and electrochemical techniques. The performance of these complexes as charge-transfer photosensitizers in nanocrystalline TiO(2)-based solar cells was studied. When complexes 5-8 anchored onto a 12 + 4 microm thick nanocrystalline TiO(2) films, very efficient sensitization was achieved (85 +/- 5% incident photon-to-current efficiencies in the visible region, using an electrolyte consisting of 0.6 M butylmethylimidazolium iodide, 0.05 M I(2), 0.1 M LiI, and 0.5 M tert-butyl pyridine in 1:1 acetonitrile + valeronitrile). Under standard AM 1.5 sunlight, the complex 8 yielded a short-circuit photocurrent density of 17 +/- 0.5 mA/cm(2), the open-circuit voltage was 720 +/- 50 mV, and the fill factor was 0.72 +/- 0.05, corresponding to an overall conversion efficiency of 8.8 +/- 0.5%.     

共存牺牲剂对染料敏化TiO_2纳米晶体系电子传输的影响

采用卟啉染料敏化TiO2纳米晶在可见光条件下(λ390 nm)进行水分解制氢.考察了不同牺牲剂———甲醇(MeOH)、三乙醇胺(TEOA)及其混合物对体系析氢效率的影响.通过荧光猝灭及光电化学性能分析发现,激发态染料与TiO2之间的电子转移极大地受到添加的牺牲剂的影响,而体系的pH值对其影响不大.     

Fabrication and photocatalytic characterizations of ordered nanoporous X-doped (X = N, C, S, Ru, Te, and Si) TiO2/Al2O3 films on ITO/glass

Transparent, ordered nanoporous TiO2/Al2O3 composite films doped with metal elements (Ru, Si, and Te) and nonmetal elements (N, C, and S) were fabricated by successive anodization and sol-gel process directly on glass substrates covered with a tin-doped indium oxide (ITO) film. The doping of ruthenium, nitrogen, carbon, and sulfur in TiO2 exhibited an enhanced effect on the absorbance, while the doping of silicon and tellurium showed little effect. Particularly, the N- and Ru-doped TiO2/Al2O3 films on ITO/glass developed an enhanced absorption red shift of 580 nm (-N) and 500 nm (-Ru). The nanoporous TiO2/Al2O3 composite film exhibited the highest photocatalytic activity in decomposing acetaldehyde under ultraviolet-light irradiation, with a value of 13 times in initial reaction rate or 7.8 times in quantum yield higher than a commercially available TiO2 material, Degussa P25. The ultraviolet-light photocatalytic activities of nanoporous TiO2/Al2O3 films were enhanced by the doping of nitrogen, carbon, and sulfur but slightly weakened by the doping of ruthenium, silicon, and tellurium. Particularly, the nanoporous N-doped TiO2/Al2O3 films exhibited effective photocatalytic activity on ultraviolet light decomposition of a highly toxic dioxin, HpCDD, and gave the highest decomposition rate of approximately 95% (via 7 h of irradiation) for the specimen with a dopant content of 1.7 wt % nitrogen.     

Single nanocrystals of anatase-type TiO2 prepared from layered titanate nanosheets: formation mechanism and characterization of surface properties

Anatase-type TiO2 single nanocrystals with boatlike, comblike, sheetlike, leaflike, quadrate, rhombic, and wirelike particle morphologies were prepared by hydrothermal treatment of a layered titanate nanosheet colloidal solution. The formation reactions and surface properties of the TiO2 nanocrystals were investigated using XRD, TEM, TG-DTA analyses, and measurements of BET specific surface area, photocatalytic activity, and ruthenium dye (N719) adsorption. The crystal morphology can be controlled by reaction temperature, pH value of reaction solution, and exfoliating agent. The titanate nanosheets were transformed to the TiO2 nanocrystals by two types of reactions. One is an in situ topotactic structural transformation reaction, and the other is a dissolution-deposition reaction on the surface. The anatase nanocrystals formed by the in situ topotactic structural transformation reaction retain the sheetlike particle morphology of the precursor, and they preferentially expose the (010) plane of anatase structure. The crystal surface of anatase nanocrystals prepared in this study showed higher photocatalytic activity and higher ruthenium dye adsorption capacity than did the Ishihara ST-01 sample, a standard anatase nanocrystal sample. The results indicated the (010) plane of the anatase structure has high photocatalytic activity and high ruthenium dye adsorption ability.     

Light-driven tyrosine radical formation in a ruthenium-tyrosine complex attached to nanoparticle TiO2

We demonstrate a possibility of multistep electron transfer in a supramolecular complex adsorbed on the surface of nanocrystalline TiO(2). The complex mimics the function of the tyrosine(Z)() and chlorophyll unit P(680) in natural photosystem II (PSII). A ruthenium(II) tris(bipyridyl) complex covalently linked to a L-tyrosine ethyl ester through an amide bond was attached to the surface of nanocrystalline TiO(2) via carboxylic acid groups linked to the bpy ligands. Synthesis and characterization of this complex are described. Excitation (450 nm) of the complex promotes an electron to a metal-to-ligand charge-transfer (MLCT) excited state, from which the electron is injected into TiO(2). The photogeneration of Ru(III) is followed by an intramolecular electron transfer from tyrosine to Ru(III), regenerating the photosensitizer Ru(II) and forming the tyrosyl radical. The tyrosyl radical is formed in less than 5 micros with a yield of 15%. This rather low yield is a result of a fast back electron transfer reaction from the nanocrystalline TiO(2) to the photogenerated Ru(III).     

Photoinduced energy transfer and charge transfer on squarylium cyanine dyes

A series of squarylium cyanine dyes (Sqs) were synthesized to explore their applications in functional devices.Preliminary investigation on the mechanism involved in these devices was carried out.Spectroscopic behavior of Sqs with porphyrin (P),8-hydroxyquinolium aluminum (Alq) and ruthenium bipyridyl complex (Ru(bipy)) in solution,in film and on nanocrystalline TiO2 was investigated,respectively.A mechanism including photoinduced energy transfer and charge transfer processes was suggested in the corresponding practical devices.By means of doping,a red organic electroluminescent device (ELD) using Sq-doped Alq as the emission layer (EML) has been developed,and the total light to electricity efficiency of nanocrystalline TiO2 electrode based on using Sq-doped Ru(bipy) as photosensitizer has been improved greatly in the whole visible region,particularly in the red area above 600 nm.     

Engineering of efficient panchromatic sensitizers for nanocrystalline TiO(2)-based solar cells.

A new series of panchromatic ruthenium(II) sensitizers derived from carboxylated terpyridyl complexes of tris-thiocyanato Ru(II) have been developed. Black dye containing different degrees of protonation [(C(2)H(5))(3)NH][Ru(H(3)tcterpy)(NCS)(3)] 1, [(C(4)H(9))(4)N](2)[Ru(H(2)tcterpy)(NCS)(3)] 2, [(C(4)H(9))(4)N](3)[Ru(Htcterpy)(NCS)(3)] 3, and [(C(4)H(9))(4)N](4)[Ru(tcterpy)(NCS)(3)] 4 (tcterpy = 4,4',4' '-tricarboxy-2,2':6',2' '-terpyridine) have been synthesized and fully characterized by UV-vis, emission, IR, Raman, NMR, cyclic voltammetry, and X-ray diffraction studies. The crystal structure of complex 2 confirms the presence of a Ru(II)N6 central core derived from the terpyridine ligand and three N-bonded thiocyanates. Intermolecular H-bonding between carboxylates on neighboring terpyridines gives rise to 2-D H-bonded arrays. The absorption and emission maxima of the black dye show a bathochromic shift with decreasing pH and exhibit pH-dependent excited-state lifetimes. The red-shift of the emission maxima is due to better pi-acceptor properties of the acid form that lowers the energy of the CT excited state. The low-energy metal-to-ligand charge-transfer absorption band showed marked solvatochromism due to the presence of thiocyanate ligands. The Ru(II)/(III) oxidation potential of the black dye and the ligand-based reduction potential shifted cathodically with decreasing number of protons and showed more reversible character. The adsorption of complex 3 from methoxyacetonitrile solution onto transparent TiO(2) films was interpreted by a Langmuir isotherm yielding an adsorption equilibrium constant, K(ads), of (1.0 +/- 0.3) x 10(5) M(-1). The amount of dye adsorbed at monolayer saturation was (n(alpha) = 6.9 +/- 0.3) x 10(-)(8) mol/mg of TiO(2), which is around 30% less than that of the cis-di(thiocyanato)bis(2,2'-bipyridyl-4,4'-dicarboxylate)ruthenium(II) complex. The black dye, when anchored to nanocrystalline TiO(2) films achieves very efficient sensitization over the whole visible range extending into the near-IR region up to 920 nm, yielding over 80% incident photon-to-current efficiencies (IPCE). Solar cells containing the black dye were subjected to analysis by a photovoltaic calibration laboratory (NREL, U.S.A.) to determine their solar-to-electric conversion efficiency under standard AM 1.5 sunlight. A short circuit photocurrent density obtained was 20.5 mA/cm(2), and the open circuit voltage was 0.72 V corresponding to an overall conversion efficiency of 10.4%.     

Engineering of a novel ruthenium sensitizer and its application in dye-sensitized solar cells for conversion of sunlight into electricity

A novel ligand 4,4'-bis(carboxyvinyl)-2,2'-bipyridine (L) and its ruthenium(II) complex [Ru(II)L(2)(NCS)(2)] (K8) were synthesized and characterized by analytical, spectroscopic, and electrochemical techniques. The performance of the K8 complex as a charge transfer photosensitizer in nanocrystalline TiO(2) based solar cells was studied. When the K8 complex anchored onto a nanocrystalline TiO(2) film, we achieved very efficient sensitization yielding 77 +/-5% incident photon-to-current efficiencies (IPCE) in the visible region using an electrolyte consisting of 0.6 M methyl-N-butyl imidiazolium iodide, 0.05 M iodine, 0.05 M LiI, and 0.5 M 4-tert-butylpyridine in a 50/50 (v/v) mixture of valeronitrile and acetonitrile. Under standard AM 1.5 sunlight, the complex K8 gave a short circuit photocurrent density of 18 +/- 0.5 mA/cm(2), and the open circuit voltage was 640 +/- 50 mV with fill factor of 0.75 +/- 0.05, corresponding to an overall conversion efficiency of 8.64 +/- 0.5%.     

Ru-TiO_2光电极的研制与性能研究

采用阳极氧化法制备Ru-TiO2光电极,通过紫外-可见漫反射吸收(UV-Vis-DRS)、X-射线衍射(XRD)和交流阻抗(EIS)对光电极的性能进行表征,探讨了氧化电压、煅烧温度、钌掺杂量的影响。结果表明:Ru掺杂后TiO2结晶更完全,光吸收强度明显提高。在HF电解液中,阳极氧化制备Ru-TiO2光电极的最佳条件为:氧化电压为20V,热处理温度600℃,钌掺杂量1%。不同条件Ru-TiO2光电极对甲基橙溶液进行脱色效果依次为:光电催化光催化电催化。     

Influence of ionic liquids bearing functional groups in dye-sensitized solar cells

Ionic liquids containing the nitrile and vinyl functional groups attached to imidazolium cations combined with various anions, e.g., iodide, bis[(trifluoromethyl)sulfonyl]imide ([TFSI]-), or dicyanamide ([N(CN)2]-), have been prepared and characterized. These ionic liquids have been successfully used as electrolytes for dye-sensitized solar cells based on nanocrystalline TiO2 with the amphiphilic ruthenium sensitizer [ruthenium (4,4'-dicarboxylic acid-2,2'-bipyridine)(4,4'-bis(p-hexyloxystyryl)-2,2'-bipyridine)][NCS]2 (coded K-19). The iodide salt was used in 3-methoxypropionitrile-based electrolytes, and the performances of both types of devices were evaluated on the basis of their photocurrent density-voltage characteristics and dark current measurements, demonstrating that the functional groups do not exert a detrimental effect on the performance. The solid-state structure of the nitrile-functionalized salt [C1C3CN(im)]I has also been established by single-crystal X-ray diffraction, revealing extensive hydrogen bonding between the cation protons and the iodide.