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Solar cells that operate efficiently under indoor lighting are of great practical interest as they can serve as electric power sources for portable electronics and devices for wireless sensor networks or the Internet of Things. Here, we demonstrate a dye-sensitized solar cell (DSC) that achieves very high power-conversion efficiencies (PCEs) under ambient light conditions. Our photosystem combines two judiciously designed sensitizers, coded D35 and XY1, with the copper complex Cu(II/I)(tmby) as a redox shuttle (tmby, 4,4′,6,6′-tetramethyl-2,2′-bipyridine), and features a high open-circuit photovoltage of 1.1 V. The DSC achieves an external quantum efficiency for photocurrent generation that exceeds 90% across the whole visible domain from 400 to 650 nm, and achieves power outputs of 15.6 and 88.5 μW cm–2 at 200 and 1,000 lux, respectively, under illumination from a model Osram 930 warm-white fluorescent light tube. This translates into a PCE of 28.9%. A dye-sensitized solar cell that has been designed for efficient operation under indoor lighting could offer a convenient means for powering the Internet of Things.

Propionitrile electrolyte solutions mixed with sulfolane or with 1-ethyl 3-methyl imidazolium tetracyanoborate (ionic liquid) are optimized for Co(bpy)(3)(3+)/Co(bpy)(3)(2+)-tmediated DSCs working at low illumination intensity. Highly-active cathode catalysts based on graphene oxide, either pure or mixed with graphene nanoplatelets or with stacked graphene fibers, can be prepared at temperatures

The dependence of the electron density and electron lifetime in nanocrystalline-TiO2 electrode on the electron back reaction with I3− in a dye-sensitized solar cell, based on a mesoporous titania (TiO2) matrix immersed in an iodine-based electrolyte, has been presented by analyzing the results of voltage decay and charge extraction measurements without modelling, without interpretation of mechanism, and without complicating calculations. This new analysis approach utilizes simple equations and basic definition of kinetics, concluding in absolute electron-density and charge-lifetime measurements. The relation of electron lifetime to open-circuit voltage indicates a peak of the long-lifetime charge at 5.5 V, which is consistent with the information of middle band suggested by Bisquert et al. (2004).

Stacked multijunction (tandem) solar cells have been prepared by mechanically stacking dye-sensitised solar cells (DSCs) and a GaAs/AlXGa(1−X)As graded solar cell (GGC) as the top and bottom cells, respectively. Three organic dyes with different absorption spectra (D131, D102 and D205) were used in the DSCs, in order to match the photocurrent density between the DSC and the GGC. Tuning the absorption range of the DSC by choosing an appropriate dye, increased the overall photovoltaic conversion efficiency due to the optimal utilisation of the solar spectrum in the individual cells. The open circuit photovoltages (VOC) of the GGC and the DSC with D131 were 1.11 V and 0.76 V, respectively, resulting in a VOC of 1.85 V and a photovoltaic conversion efficiency of 7.63% for the tandem cell. Although the overall conversion efficiency has not exceeded that of the GGC (7.66%), these tandem cells provide adequate VOC values for water splitting applications.

The high molar extinction coefficient heteroleptic ruthenium dye, NaRu(4,4'-bis(5-(hexylthio)thiophen-2-yl)-2,2'-bipyridine) (4-carboxylic acid-4'-carboxylate-2,2'-bipyridine) (NCS)(z), exhibits certified 5% electric power conversion efficiency at AM 1.5 solar irradiation (100 mWcm(-2)) in a solid-state dye-sensitized solar cell using 2,2',7,7'-tetrakis-(N,N-dipmethoxyphenylamine)-9,9'-spirobifluorene (spiro-MeOTAD) as the organic hole-transporting material. This demonstration elucidates a class of photovoltaic devices with potential for low-cost power generation. (C) 2010 Elsevier Ltd. All rights reserved.

Solar energy is a promising solution to global energy-related problems because it is clean, inexhaustible and readily available. However, the deployment of conventional photovoltaic cells based on silicon is still limited by cost, so alternative, more cost-effective approaches are sought. Here we report a bifacial dye-sensitized solar cell structure that provides high photo-energy conversion efficiency (∼6%) for incident light striking its front or rear surfaces. The design comprises a highly stable ruthenium dye (Z907Na) in combination with an ionic-liquid electrolyte and a porous TiO2 layer. The inclusion of a SiO2 layer between the electrodes to prevent generation of unwanted back current and optimization of the thickness of the TiO2 layer are responsible for the enhanced performance. Low-cost, efficient solar cells are sought as an alternative to silicon photovoltaics. Here a dye-based bifacial solar cell that is capable of efficient generation of electricity for light incident on either its front or rear face is demonstrated.

Techniques of TiO2 film fabrication for dye-sensitized solar cells having a conversion efficiency of global air mass 1.5 (AM 1.5, 1000 W/m(2)) solar light to electric power over 10% are reported. Newly implemented fabrication technologies consist of pre-treatment of the working photoelectrode by TiCl4, variations in layer thickness of the transparent nanocrystalline-TiO2 and applying a topcoat light-scattering layer as well as the adhesion of an anti-reflecting film to the electrode's surface. TiCl4 treatments induce improvements in the adhesion and mechanical strength of the nanocrystalline TiO2 layer. Optimization of the thickness of the TiO2 layer, acting as the working electrode, affects both the photocurrent and the photovoltage of the devices. Covering of the TiO2 photoanode by an anti-reflecting film results in enhancement of the photocurrent. Each of these components of film fabrication exerts a significant influence on the overall photovoltaic parameters of the devices resulting in improvements in the net energy conversion performance. (C) 2007 Elsevier B.V. All rights reserved.

Dye-sensitized solar cells have been fabricated with different kinds of TiO2 films including SiO2 coated and bare TiO2 microparticles as light-scattering layer (LSL). Results show that the LSL barely affects the cell's dark current, whereas under illumination, it made a significant contribution to the total photocurrent. Photo-voltage decay measurements performed under bias illumination show the density of electronic states (DOS) of the LSL to be two times smaller than that of a transparent nanoparticle layer (TNL). Strikingly, DSCs fabricated from a 4.5μm thick LSL alone showed a conversion efficiency of 5% despite of being pale pink in color. This impressive performance is attributed to light containment in the LSL and a low density of defect electronic states.

Reference LPI-ARTICLE-2006-008doi:10.1002/adma.200502540View record in Web of Science Record created on 2006-05-03, modified on 2016-08-08

Reference LPI-ARTICLE-2006-037doi:10.1002/pip.683View record in Web of Science Record created on 2006-11-09, modified on 2017-05-12

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.

We report a combined experimental and computational study of several ruthenium(II) sensitizers originated from the [Ru(dcbpyH(2))(2)(NCS)(2)], N3, and [Ru(dcbpyH(2))(tdbpy)(NCS)(2)], N621, (dcbpyH(2) = 4,4'-dicarboxy-2,2'-bipyridine, tdbpy = 4,4'-tridecyl-2,2'-bipyridine) complexes. A purification procedure was developed to obtain pure N-bonded isomers of both types of sensitizers. The photovoltaic data of the purified N3 and N621 sensitizers adsorbed on TiO(2) films in their monoprotonated and diprotonated state, exhibited remarkable power conversion efficiency at 1 sun, 11.18 and 9.57%, respectively. An extensive Density Functional Theory (DFT)-Time Dependent DFT study of these sensitizers in solution was performed, investigating the effect of protonation of the terminal carboxylic groups and of the counterions on the electronic structure and optical properties of the dyes. The calculated absorption spectra are in good agreement with the experiment, thus allowing a detailed assignment of the UV-vis spectral features of the two types of dyes. The computed alignments of the molecular orbitals of the different complexes with the band edges of a model TiO(2) nanoparticle provide additional insights into the electronic factors governing the efficiency of dye-sensitized solar cell devices.

A novel synthetic route for preparation of amphiphilic heteroleptic ruthenium(II) complexes of the type [Ru(H 2 dcbpy)Cl(cymene)]NO 3 ( 1 ) [Ru(H 2 dcbpy)(dmbpy)(NCS) 2 ] ( 2 ), [Ru(H 2 dcbpy)(dhbpy)(NCS) 2 ] ( 3 ) [Ru(H 2 dcbpy)(dnbpy)(NCS) 2 ] ( 4 ) and [Ru(H 2 dcbpy)(dtdbpy)(NCS) 2 ] ( 5 ) have been developed starting from dichloro( p -cymene)ruthenium(II) dimer. The performance of these complexes as charge-transfer photosensitizers in nanocrystalline TiO 2 -based solar cells was studied. When anchored complexes 2 – 5 onto a 12+4 μm thick nanocrystalline TiO 2 films achieve very efficient sensitization over 85±5% incident photon-to-current efficiencies (IPCEs) in the visible region. Under standard AM 1.5 sunlight, using an electrolyte consisting of 0.6 M BMII; 0.05 M I 2 ; 0.1 M LiI; 0.5 M tert -butyl pyridine in 1:1 acetonitrile + valeronitrile the films yielded a short circuit photocurrent density of 16±0.5 mA/cm 2 and the open circuit voltage was 700±50 mV and a fill factor of 0.75±0.05, corresponding to an overall conversion efficiency of 8.6%. Solar cells based on amphiphilic sensitizers show remarkable stability under both thermal stress and light soaking matching the durability criteria applied to silicon solar cells for outdoor applications.

FTIR spectra of [Ru(dcbpyH2)2(NCS)2] (N3), (Bu4N)2[Ru(dcbpyH)2(NCS)2] (N719), and (Bu4N)4[Ru(dcbpy)2(NCS)2] (N712) complexes measured as solid samples in photoacoustic mode display fine resolution of IR bands and exhibit differences between the cis and the trans carboxylic acid groups. The interaction between N3, N719, and N712 sensitizers with nanocrystalline TiO2 film was investigated by ATR-FTIR spectroscopy. The data show that these complexes are being anchored onto the TiO2 surface in bridging coordination mode using two out of their four carboxylic acid groups, which are trans to the NCS ligand. The effect of protons on both the short circuit photocurrent and the open circuit photovoltage of dye-sensitized nanocrystalline solar cells was scrutinized. For the standard electrolyte formulation employed and TiCl4 treated mesoporous TiO2 films, the monoprotonated form of the N3 dye exhibited superior power conversion efficiency under AM 1.5 sun compared to the four, two, and zero proton sensitizers.

The woven fabric containing electrochemically platinized tungsten wire is an affordable flexible cathode for liquid-junction dye-sensitized solar cells with the I3(-)/I(-) redox mediator and electrolyte solution consisting of ionic liquids and propionitrile. The fabric-based electrode outperforms the thermally platinized FTO in serial ohmic resistance and charge-transfer resistance for triiodide reduction, and it offers comparable or better optical transparency in the visible and particularly in the near-IR spectral region. The electrode exhibits good stability during electrochemical loading and storage at open circuit. The dye-sensitized solar cells with a C101-sensitized titania photoanode and either Pt-W/PEN or Pt-FTO cathodes show a comparable performance.

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%.

TaON was found to be ca. 20 times more active as a visible light activated photocatalyst for the oxidation of methanol, when compared to the well studied UV-visible activated TiO2 (P25) catalyst.

A nanocrystalline TiO2 (anatase) nanosheet ex- posing mainly the (001) crystal faces was tested as photo- anode material in dye-sensitized solar cells. The nanosheets were prepared by hydrothermal growth in HF medium. Good-quality thin films were deposited on F-doped SnO2 support from the TiO2 suspension in ethanolic or aqueous media. The anatase (001) face adsorbs a smaller amount of the used dye sensitizer (C101) per unit area than the (101) face which was tested as a reference. The corresponding solar cell with sensitized (001)-nanosheet photoanode exhibits a larger open-circuit voltage than the reference cell with (101)-terminated anatase nanocrystals. The voltage enhancement is attributed to the negative shift of flatband potential for the (001) face. This conclusion rationalizes earlier works on similar systems, and it indicates that careful control of experimental conditions is needed to extract the effect of band energetic on the current/voltage character- istics of dye-sensitized solar cell.

A round robin for the performance of roll-to-roll coated flexible large-area polymer solar-cell modules involving 18 different laboratories in Northern America, Europe and Middle East is presented. The study involved the performance measurement of the devices at one location (Risø DTU) followed by transportation to a participating laboratory for performance measurement and return to the starting location (Risø DTU) for re-measurement of the performance. It was found possible to package polymer solar-cell modules using a flexible plastic barrier material in such a manner that degradation of the devices played a relatively small role in the experiment that has taken place over 4 months. The method of transportation followed both air-mail and surface-mail paths.

An indoline dye (D205), the synthesis method of which is disclosed in this report, gave high-efficiency organic dye-sensitized solar cells (9.52%) using an anti-aggregation reagent (chenodeoxycholic acid).

A series of CN-bridged trinuclear Ru complexes of the general structure [RuL2(μ-(CN)Ru(CN)L2′)2] where L is 2,2′-bipyridine-4,4′-dicarboxylic acid and L′ is 2,2′-bipyridine (1)2,2′-bipyridine-4,4′-dicarboxylic acid (2), 4,4′-dimethyl-2,2′-bipyridine (3), 4,4′-diphenyl-2,2′-bipyridine (4), 1,10-phenanthroline (5), and bathophenanthrolinedisulfonic acid (6) have been synthesized, and their spectral and electrochemical properties investigated. The two carboxylic functions on the 2,2′-bipyridine ligand L serve as interlocking groups through which the dye is attached at the surface of TiO2 films having a specific surface texture. The role of these interlocking groups is to provide strong electronic coupling between the π* orbital of the 2,2′-bipyridine and the 3d-wave-function manifold of the conduction band of the TiO2, allowing the charge injection to proceed at quantum yields close to 100 %. The charge injection and recombination dynamics have been studied with colloidal TiO2, using laser photolysis technique in conjunction with time-resolved optical spectroscopy. Photocurrent action spectra obtained from photo-electrochemical experiments with these trinuclear complexes cover a very broad range in the visible, making them attractive candidates for solar light harvesting. Monochromatic incident photon-to-current conversion efficiencies are strikingly high exceeding 80% in some cases. Performance characteristics of regenerative cells operating with these trinuclear complexes and ethanolic triiodide/iodide redox electrolyte have been investigated. Optimal results were obtained with complex 1 which gave a fill factor of 75 % and a power conversion efficiency of 11.3% at 520 nm.

This paper presents an overview of the research carried out by a European consortium with the aim to develop and test new and improved ways to realise dye-sensitized solar cells (DSC) with enhanced efficiencies and stabilities. Several new areas have been explored in the field of new concepts and materials, fabrication protocols for TiO2 and scatterlayers, metal oxide blocking layers, strategies for co-sensitization and low temperature processes of platinum deposition. Fundamental understanding of the working principles has been gained by means of electrical and optical modelling and advanced characterization techniques. Cost analyses have been made to demonstrate the potential of DSC as a low cost thin film PV technology. The combined efforts have led to maximum non-certified power conversion efficiencies under full sunlight of 11% for areas < 0 center dot 2 cm(2) and 10 center dot 1% for a cell with an active area of 1 center dot 3 cm(2). Lifetime studies revealed negligible device degradation after 1000hrs of accelerated tests under thermal stress at 80 degrees C in the dark and visible light soaking at 60 degrees C. An outlook summarizing future directions in the research and large-scale production of DSC is presented.

High-efficiency flexible dye-sensitized solar cells were fabricated with a Ti-metal foil substrate for photo anode and using a Pt-electrodeposited counter electrode on ITO/polyethylene naphthalate (ITO/PEN); these devices were characterized by incident photon-to-current efficiency (IPCE), optical transmittance and electrical impedance spectroscopy.

The Pluronic P123 templated mesoporous TiO2 film was grown via layer-by-layer deposition and characterized by a novel methodology based on the adsorption of n-pentane. Multiple-layer depositions did not perturb the mesoporous structure significantly. Our TiO2 film was sensitized by a newly developed Ru-bipyridine dye (N945) and was applied as a photoanode in dye-sensitized solar cell. The 1-microm-thick mesoporous film, made by the superposition of three layers, showed enhanced solar conversion efficiency by about 50% compared to that of traditional films of the same thickness made from randomly oriented anatase nanocrystals.

The further morphological investigation of nanocrystalline TiO2 films, which sensitized by suitable transition metal complexes forming a new type of molecular photovoltaic systems, the studies of new films and a new Co complexes are presented herein. Scanning electron microscopy, X-ray single crystal and powder diffraction as well as X-ray diffraction at low glancing angles using synchrotron radiation have been used. The morphology of electro- and thermodeposited Pt-layers on TCO (a), polymorphic composition of films (b), possible geometry of location of complex dye molecules on the exposed most faces of TiO2 microcrystals (c) and the crystal structure of a Co(II) complex solvated by electrolyte 4- methyl-1,3-dioxolan-2-on as a precursor of the corresponding redox-system (d) are discussed.© (1993) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Multijunction stacked (tandem) solar cells can increase the overall photovoltaic conversion efficiency by optimal utilization of the solar spectrum in individual cells. We demonstrate that a photovoltaic tandem cell comprising a nanocrystalline dye-sensitized solar cell as a top cell for high-energy photons and a copper indium gallium selenide thin-film bottom cell for lower-energy photons produces AM 1.5 solar to electric conversion efficiencies greater than 15%.

Carbon black was employed as the catalyst for triiodide reduction on fluorine-doped tin oxide glass substrates (FTO-glass) used as counter electrodes in platinum-free dye-sensitized solar cells. The fill factors were strongly dependent on the thickness of the carbon layer, and the light energy conversion efficiency also increased up to a thickness of 10 μm. The charge-transfer resistance (R ct ) of the carbon counter electrode decreased with the thickness of the carbon layer. The R ct for the thicker carbon layer is less than three times that for the platinized FTO-glass. The highest cell efficiency was 9.1% under 100 mW cm -2 light intensity (1 sun AM 1.5 light, J sc = 16.8 mA cm -2 , V oc = 789.8 mV, fill factor = 0.685).

The ruthenium complex bis-tetrabutylammonium cis-dithiocyanato-N,N′-bis-2,2′-bipyridine-4-carboxylic acid, 4′-carboxylate ruthenium(II), N-719, was found to block the dark current of dye sensitized solar cells (DSC), based on mesoporous TiO2 films deposited on a F-doped tin oxide electrode and the effect was compared to surface treatment by TiCl4 and the introduction of a compact TiO2 blocking layer.

We report an analysis of the influence of acid/base conditions employed in the synthesis of TiO2 nanoparticles upon the performance of dye sensitised photoelectrochemical solar cells fabricated from these particles. The functional properties of the TiO2 nanoparticles in these devices are investigated by potential step chronoamperometry, transient laser spectroscopy, and photovoltaic device characterisation. We find that base peptization conditions employed in the sol–gel fabrication of the TiO2 nanoparticles result in a reduction in film electron density under negative applied bias, correlated with slower interfacial recombination losses and a higher device open circuit voltage.

Reference LPI-ARTICLE-1987-021View record in Web of Science Record created on 2006-02-21, modified on 2017-05-12

Reference LPI-ARTICLE-1988-021doi:10.1021/ja00219a068View record in Web of Science Record created on 2006-02-21, modified on 2017-05-12

The energy conversion efficiency of photoelectrochemical solar cells using those oxide semiconductor electrodes which are stable in contact with aqueous electrolytes is low because their wide band gaps do not permit a photoresponse to the visible spectrum. By adsorption of a sufficient quantity of a charge-transfer dye with intimate contact to the semiconductor, the electrode can be sensitised to visible radiation. Titanium dioxide electrodes were derivatised by attached ruthenium bis- and tris- bipyridyl and zinc porphyrin dyes and their efficiency as photoelectrochemical solar cell electrodes is reported.

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.

Ruthenium(II) complexes [Ru(L2)(NCS)2] (K8) and [Ru(L)(L9)(NCS)2] (K9) (where L = 4,4′-bis(carboxyvinyl)-2,2′-bipyridine and L9 = 4,4′-dinonyl-2,2′-bipyridine) were synthesized and characterized by spectroscopic and electrochemical techniques. The performance of K8 and K9 complexes as charge transfer photosensitizers in nanocrystalline TiO2-based solar cells was investigated. These complexes when anchored onto TiO2 films exhibit very efficient sensitization yielding 75 ± 5% incident photon-to-current efficiencies (IPCE) in the visible region using an electrolyte consisting of 0.6 M methyl-N-butyl imidazolium iodide, 0.05 M iodine, 0.1 M LiI and 0.5 M tert-butylpyridine in 50/50 (v/v) mixture of valeronitrile and acetonitrile. At one sun, the K8 complex gave a short circuit photocurrent density of 18 ± 0.5 mA/cm2, the open circuit voltage 640 ± 50 mV and fill factor of 0.75 ± 0.05, corresponding to an overall conversion efficiency of 8.64 ± 0.5%. Under similar conditions, the K9-sensitized solar cell gave a photocurrent density of 16.5 ± 0.5 mA/cm2, 666 ± 50 mV open circuit potential and 0.71 ± 0.05 fill factor yielding 7.81% ± 0.6% efficiency.

Reference LPI-ARTICLE-2007-002doi:10.1016/j.jphotochem.2006.06.028View record in Web of Science Record created on 2007-01-09, modified on 2016-08-08

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%.

A preparation technique of TiO2 screen-printing pastes from commercially-available powders has been disclosed in order to fabricate the nanocrystalline layers without cracking and peeling-off over 17 µm thickness for the photoactive electrodes of the dye-sensitised solar cells. A conversion efficiency of 8·7% was obtained by using a single-layer of a semi-transparent-TiO2 film. A conversion efficiency of 9·2% was obtained by using double-layers composed of transparent and light-scattering TiO2 films for a photon-trapping system. Copyright © 2007 John Wiley & Sons, Ltd.

cis-X 2 Bis(2,2'-bipyridyl-4,4'-dicarboxylate)ruthenium(II) complexes (X=Cl - , Br, I - , CN - , and SCN - ) were prepared and characterized with respct to their absorption, luminescence, and redox behavior. They act as efficient charge-transfer sensitizers for nanocrystalline TiO 2 films (thickness 8-12 μm) of very high internal surface area (roughness factor ca. 1000), prepared by sintering of 15-30-nm colloidal titania particles on a conducting glass support. The performance of cis-di(thiocyanato)bis(2,2'-bipyridyl-4,4'-dicarboxylate)ruthenium(II) (1) was found to be outstanding and is unmatched by any other known sensitizer

A ruthenium complex trans-[Ru(L)(NCS)2], L = 4,4' ''-di-tert-butyl-4',4' '-bis(carboxylic acid)-2,2':6',2' ':6' ',2' ''-quaterpyridine (N886), was synthesized and characterized by spectroscopic and electrochemical methods. The absorption spectrum of the N886 complex shows metal-to-ligand charge-transfer transitions in the entire visible region and quasi-reversible oxidation and reduction potentials at E(1/2) = +0.38 and -1.92 V vs ferrocene, respectively. The electronic spectra of the N886 complex were calculated by density functional theory (DFT)-time-dependent DFT, which qualitatively reproduces the experimental absorption spectra for both the protonated and deprotonated species. From the analysis of the computed optical transitions of N886, we assign its absorption bands as mixed Ru/SCN-to-quaterpyridine charge-transfer transitions, which extend from the near-IR to the UV regions. The panchromatic response of the N886 complex renders it as a suitable sensitizer for solar energy conversion applications based on titanium dioxide mesoporous electrodes. The preliminary results using the N886 complex as a sensitizer in a dye-sensitized solar cell, with an electrolyte containing 0.60 M butylmethylimidazolium iodide, 0.03 M I2, and 0.50 M tert-butylpyridine in a mixture of acetonitrile and valeronitrile (volume ratio 1:1), show 40% incident photon-to-current efficiencies, yielding under standard AM 1.5 sunlight a short-circuit photocurrent density of 11.8 +/- 0.2 mA/cm(2), an open-circuit voltage of 680 +/- 30 mV, and a fill factor of 0.73 +/- 0.03, corresponding to an overall conversion efficiency of 5.85%.

TiO2 dye-sensitized quasi-solid-state solar cells have been constructed by employing a nanocomposite organic/inorganic gel electrolyte made by the sol−gel method. The nanocomposite gel is based on silica while its organic subphase is a mixture of a surfactant (Triton X-100), an organic solvent (propylene carbonate), iodine, and 1-methyl-3-propylimidazoliumiodide, which is an ionic liquid (molten salt). The last two components produce a I3-/I- redox couple. Improved results were obtained by also adding N-methylbenzimidazole. Time-resolved luminescence quenching analysis, dark dc conductivity measurements, and cell efficiency measurements were used to determine the optimal composition of the gel for maximum cell efficiency, which in the present case was 5.4%.

Reference LPI-ARTICLE-1999-019doi:10.1149/1.1391698View record in Web of Science Record created on 2006-02-21, modified on 2017-05-12

The concept of a tandem hybrid concentrator solar module was demonstrated from a dye-sensitized TiO2 solar cell (DSSCs) and a silicon p-n junction solar cell. The test system employed DSSC and Si cells with indoor AM1.5G efficiencies of 9.1 and 18.1%, respectively. Two different optical filters were used to selectively reflect and concentrate near-infrared light from the DSSC onto the Si cell. On the basis of outdoor testing in a 2 x concentrator reflector arrangement, the tandem system generated 93 and 96% of the output power of directly illuminated Si cells under altostratus/cirrostratus and clear sky irradiances, respectively, despite a DSSC-to-Si active area ratio of only 0.92. Similar performance is expected at higher (5-10 x) concentration ratios. The hybrid arrangement of visible- and IR-absorbing solar cells addresses the problem of lower performance of conventional concentrators under diffuse irradiance conditions. These proof-of-concept results suggest that system level efficiencies approaching 20% should be achievable.

Reference LPI-ARTICLE-1988-002doi:10.1021/ja00212a033View record in Web of Science Record created on 2006-02-21, modified on 2017-05-12

Reference LPI-ARTICLE-1988-021doi:10.1021/ja00219a068View record in Web of Science Record created on 2006-02-21, modified on 2017-05-12