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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+ -mediated 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 ≤200 °C. The catalytic layers are well adhering to the substrates, i.e. to FTO or to stainless-steel surfaces, both the flat steel sheet and the steel wires in woven fabric consisting of transparent polyester (PEN) fibers in warp and stainless steel wires in weft (Sefar B23). The dye-sensitized solar cells with various cathodes, fabricated either from Pt or from optimized graphene-based catalysts, and supported by either FTO or by stainless-steel/PEN fabric, show similar solar conversion efficiencies between 6.9 and 7.9% at 0.25 sun illumination. [ABSTRACT FROM AUTHOR]

A nanocrystalline TiO (anatase) nanosheet exposing mainly the (001) crystal faces was tested as photoanode 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 SnO support from the TiO 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 characteristics of dye-sensitized solar cell. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Abstract: 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/m2) 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. [Copyright &y& Elsevier]

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 TiO2 was performed. The calculations point out that the top three frontier-filled orbitals have essentially ruthenium 4d (t2g in the octahedral group) character with sizable contribution coming from the NCS ligand orbitals. Most critically the calculations reveal that, in the TiO2-bound N945 sensitizer, excitation directs charge into the carboxylbipyridine ligand bound to the TiO2 surface. The photovoltaic data of the N945 sensitizer using an electrolyte containing 0.60 M butylmethylimidazolium iodide, 0.03 M I2, 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 °C. [ABSTRACT FROM AUTHOR]

We report a combined experimental and computational study of several ruthenium(II) sensitizers originated from the [Ru(dcbpyH2)2(NCS)2], N3, and [Ru(dcbpyH2)(tdbpy)(NCS)2], N621, (dcbpyH2 = 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 TiO2 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 TiO2 nanoparticle provide additional insights into the electronic factors governing the efficiency of dye-sensitized solar cell devices. [ABSTRACT FROM AUTHOR]

Examines the engineering of panchromatic sensitizers for nanocrystalline TiO[sub 2]-based solar cells. Absorption and emission maxima of black dye; Presence of thiocyanates ligands.