Benzonitrile based electrolytes for best operation of dye sensitized solar cells

The beneficial effect of benzonitrile as electrolyte solvent in Dye Sensitized Solar Cells (DSSCs) is demonstrated. The very low vapour pressure of benzonitrile (133 Pa @ 25 °C) ensures long-term stability to the cells and efficiency values were found around 8% for more than 1300 hours. These results were obtained by using commercial P90 titania photoanodes sensitized by N719 dye, i.e., by making use of common and low priced materials. In this way, neither complex dyes nor passivating agents are required to maintain satisfactory efficiencies in a non-volatile electrolyte solvent as 3-methoxypropionitrile, as reported in literature. The results of this work have to be considered an important step towards an easy and economic fabrication of devices with stable performances for commercially convenient periods. Twelve electrolytes were examined: 9 of them had benzonitrile as solvent, different ratios I-/I2 and different ionic liquid iodide salts whereas, for comparison, one electrolyte in acetonitrile and another in 3-methoxypropionitrile were studied. As reference, the redox couple I3-/I - in benzonitrile without additives was also examined. The electrolytes were characterized by specific conductivity vs. temperature, diffusion coefficient of I3 - and redox potential of the I3-/I- couple measurements. Efficiency, dark current and IPCE of DSSCs were determined for each electrolyte. © 2014 Elsevier B.V. All rights reserved

Nanostructured Porous Film of Doped TiO2-Anatase Semiconductor for Dye Sensitized Solar Cells (DSSCs)

Some results dealing with the synthesis, characterization and functional properties, as DSSC photo-anode active material, of solid solutions of nanostructured oxide materials hierarchically organized will be presented. The host lattice is TiO2-anatase and solute is a metal cation aliovalent with respect to Ti (IV). The scope of this work is to modify usefully the band structure of anatase with respect to the electronic levels of the light harvesting dye and to improve its electronic conductivity due to the creation of donor or acceptor levels. The final objective is to increase the DSSC conversion yield through searching for the better electronic coupling TiO2-anatase/dye since this is one of the necks that influence the whole efficiency of a DSSC. Another cause of the lack of efficiency is the electron-hole recombination in the TiO2-anatase film and we obtained satisfactory results [1] by TiO2-anatase/MWCNT nanocomposites that behave as Schottky junctions being multi walled carbon nanotubes (MWCNT) electronic conductors. In this way, the probability of recombination is reduced since electron paths shorter than the electron diffusion length in the semiconductor are created. The results obtained by doping TiO2-anatase with Nb5+ and Sc3+ will be the object of our contribution with the following items: • Synthesis of doped nanostructured TiO2-anatase with related structural and morphological characterizations; • Characterization of the electronic properties with respect pure TiO2-anatase through the flat band potential and carrier concentration measurements by the Mott-Schottky technique and band gap via diffuse reflectance; • Characterization and testing of our DSSCs realized with photo-anodes containing the above doped TiO2-anatase nanostructured materials

Effect of different lead precursors on perovskite solar cell performance and stability

We present the use of halide (PbCl2) and non-halide lead precursors (Pb(OAc)2 (OAc = CH3CH2COO−), Pb(NO3)2, Pb(acac)2 (acac = (CH3COCHCOCH3)−) and PbCO3) for the preparation of perovskite solar cells. We have confirmed by X-ray diffraction the growth of CH3NH3PbI3 in all the analyzed cases, except for PbCO3, independently of the lead precursor used for the synthesis of the perovskite. In addition, different cell configurations, thin films and mesoporous scaffolds, TiO2 or Al2O3, have also been prepared. We have observed that the lead precursor has a strong influence on the structural properties of perovskite (grain size), as well as on the solar cell performance. Photovoltaic conversion efficiencies comparable to those achieved when using the commonly employed PbCl2 have been obtained with Pb(OAc)2 as a lead source. Stability studies of the perovskite films and devices have also been carried out, which demonstrate that the lead precursor also plays a role. The stability is not only strongly affected by atmosphere and illumination conditions, but also by the lead precursor employed for the perovskite synthesis. These results highlight that other lead sources, different to the commonly used PbCl2 and PbI2, are also suitable for the development of PSCs, opening a new way for device performance optimization.This work was supported by MINECO of Spain under project MAT2013-47192-C3-1-R, Universitat Jaume I project 12I361.01/1, E.M.-M thanks the Ramón y Cajal program, and R.S.S. thanks the FP7 European project ALLOXIDE (309018)

Electrodeposition of thin solid films on gold from a choline chloride-urea electrolyte

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Electrochemical formation and stability of copper selenide thin films in the choline chloride-urea deep eutectic solvent at gold electrode

The electrodeposition of copper-selenium binary compounds on gold electrode was investigated in the choline chloride – urea (ChCl-U) deep eutectic solvent at 110 °C. Cyclic voltammetry and potentiostatic deposition followed by stripping voltammetries were employed to gain thermodynamic insights pointing to the formation of Cu2Se, which is supported by X-Ray Photoelectron Spectroscopy. The electrochemical stability domain of the compound is about 900 mV (from ≈−0.81 V to ≈+0.07 V vs. a silver quasi-reference electrode) and is consistent with the thermodynamics of induced co-deposition. The domain is limited at positive potentials by the oxidation to Se(0) and at negative potentials by the reduction to Cu(0). While copper is readily deposited on the gold electrode, the electrodeposition of selenium requires a significant overpotential. As a consequence, copper is kinetically favoured in the co-deposition and is present in its pure form at short deposition times. This is circumvented by using longer deposition times or more negative potentials. Photoelectrochemical measurements show that the as-deposited compound behaves as a p-type semiconductor.info:eu-repo/semantics/publishe

Efficiency improvement of DSSC photoanode by scandium doping of mesoporous titania beads

Solid solutions of scandium in anatase as semiconductor material for DSSC photoanodes were prepared by the controlled hydrolysis of titanium(IV) isopropoxide and scandium(III) isopropoxide in hydroalcoholic medium. The final powder was constituted by mesoporous anatase beads doped with Sc. A superstructure characterizes the beads, which are spherical at the microscopic level (?650 nm) and rice-grain-shaped at the nanoscopic level (?20 nm). The BJH pore size distribution and BET surface area of the powder beads were found depending from the Sc content ranging the peak of the former between 7 and 25 nm and between 65 and 128 m2 g–1 the latter. Data obtained by XRD and EXAFS confirm that we are dealing with real solid solutions with ScTi substitution defects. The electronic properties of the synthesized semiconductor material as a function of Sc doping were investigated by the measure of the flat band potential, band gap, and deep levels. In the range 0.0–1.0 at. % of Sc, the flat band energy changes from ?4.15 to ?4.07 eV, whereas the band gap height increases by 0.03 eV. The presence of Sc modifies heavily the cathodoluminescence spectrum of anatase at the lowest concentration too. Several DSSCs with photoanodes at different Sc doping were tested both under solar simulator and in the dark. The maximum efficiency of 9.6% was found at 0.2 at. % of Sc in anatase that is 6.7% higher with respect to the DSSCs with pure anatase