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The presence of a liquid electrolyte in dye-sensitized solar cells (DSSCs) is known to limit the time stability of these devices due to leakage and evaporation phenomena. To overcome this issue, gel-state electrolytes may represent a good solution in order to maintain stability and good performances, albeit at lower costs. In the present work, two different kinds of gel-electrolytes, based on poly (methyl methacrylate) (PMMA) and nanoclay agents, were investigated in DSSC-devices sensitized using β-substituted Zn-porphyrins (namely ZnPC4 and ZnPC12) with enveloping alkoxy chains of different lengths, able to produce a coverage of the photoanode surface. The highest power conversion efficiency (PCE) values equal to 1.06 ± 0.04% and 1.55 ± 0.26% were obtained for ZnPC12 (with longer alkoxy chains) with PMMA- and nanoclay-based electrolytes respectively. The properties of the photoanode/electrolyte interface as well as the influence of the gelling agents on the final properties of the obtained devices were thoroughly characterized. [ABSTRACT FROM AUTHOR]

A set of three new Ru(II) polypyridyl complexes decorated with 5-aryl tetrazolato ligands (R–CN4)−, (D series, namely D1, D3 and D4), is presented herein. Whereas complex D1 represents the pyrazinyl tetrazolato analogue of a previously reported Ru(II) complex (D2) with the general formula cis-[(dcbpy)2Ru(N^N)]+, in which dcbpy is 2,2′-bipyridine-4,4′-dicarboxylic acid and N^N is the chelating 2-pyridyl tetrazolato anion, the design of the unprecedented Ru(II) species D3 and D4 relied upon a completely different architecture. More specifically, the molecular structure of thiocyanate-based species cis-[(dcbpy)2Ru(NCS)2], that is typically found in benchmark Ru(II) dyes for dye sensitized solar cell (DSSCs), was modified with the replacement of two of the –NCS ligands in favour of the introduction of 5-aryl tetrazolato anions, such as the deprotonated form of 5-(4-bromophenyl)-1H-tetrazole, for complex D3 and 5-(4-cyanophenyl)-1H-tetrazole in the case of complex D4. To streamline the behavior of the D series of Ru(II) complexes as photosensitizers for DSSCs, an in-depth analysis of the excited state properties of D1, D3 and D4 was performed through TDDFT calculations and TDAS (nanosecond transient difference absorption spectroscopy). The obtained results highlight a trend that was confirmed once D1, D3 and D4 were tested as photosensitizers for DSSC under different conditions. Along the series of the Ru(II) complexes, the neutrally charged species D3 and D4 displayed the best photovoltaic performances. [ABSTRACT FROM AUTHOR]

[Display omitted] • The electrochemical properties of seawater electrolytes were investigated. • Dye-Sensitized Solar Cells based on seawater electrolytes were prepared and tested. • A photoconversion was increased of 23% with seawater instead water electrolytes. • The charge-transfer reaction mechanisms are influenced by the natural ions inside seawater electrolyte. In this work, dye-sensitized solar cells containing seawater-based electrolytes were realized and investigated. The influence of the seawater composition on the electrochemical properties of the iodide/triiodide redox mediator was determined. High triiodide diffusion coefficient and ionic conductivity were assessed for seawater electrolytes through cyclic and linear voltammetry and impedance spectroscopy. Moreover, a notable influence of the seawater electrolyte on the charge transfer mechanism at the photoanode/dye/electrolyte interfaces was observed and deeply discussed. The ions, naturally present into seawater, reduce the charge recombination mechanism at the photoanode/electrolyte interface and promote a downward shift of the TiO 2 conduction band, thus increasing the final DSSC efficiencies of 23% if compared with traditional devices containing water. The best seawater-based solar cell provides a photo-electrical conversion efficiency equal to 0.37% with 1.09 mA cm−2 as short circuit current density. To the best of our knowledge, this is the first time that seawater is used as a key component for an energy production technology and the obtained results show the great potentiality of this green and recyclable element. [ABSTRACT FROM AUTHOR]

The development of new materials based on abundant elements, reduced toxicity is today crucial for the next generation of energy device. Titanium-doped hydroxyapatite (TiHA) was tested for the first time as photoanode material for Dye – Sensitized Solar Cells (DSSCs). The chemical composition and energy structure of TiHA powders with increasing titanium content (5 wt%, 10 wt% and 15 wt%) were extensively characterized by surface electron spectroscopies, XPS and UPS. Their compatibility with conventional ruthenium-based dyes molecules was also assessed, producing considerable uptake. TiHA films were produced by screen-printing technique and XRD analyses confirm the presence of apatitic structure. The film properties were completely determined by optical, morphological (FE–SEM) and functional characterizations. Finally, TiHA-based DSSCs were assembled and their photovoltaic performance were assessed. The best efficiency, equal to 0.14%, was obtained for the TiHA containing 15 wt% of titanium. These results open the path for the possible application of doped hydroxyapatite as novel materials for energy conversion systems. [ABSTRACT FROM AUTHOR]

Abstract The chemical complexity of traditional Dye Sensitized Solar Cells (DSSCs) electrolyte requires the development of high selectivity and catalytic counter-electrode (CE) materials for the triiodide target molecule. In this work is reported for the first time that molecularly imprinted polypyrrole (MIP-PPy) can help to overcome these challenges. Different template molecules such as 2-aminoacetic acid (Glycine) and L-2-aminopropionic acid (l -Alanine) are considered during the electropolymerization process in order to verify the application of MIP-PPy as CE. The use of low concentration of Glycine leads to a MIP-PPy film exhibiting higher catalytic activity and electrochemical properties on triiodide reduction than the non-imprinted polypyrrole (NIP-PPy) one. Gel-state DSSCs based on MIP materials were prepared and tested and the optimized MIP-PPy CE with Glycine as template showed an increase of around 20% of the power conversion efficiency and a reduction of 50% of the charge transfer resistance in comparison with the cells based on NIP-PPy. These results demonstrate the possibility to enhance the catalytic properties of PPy CE without adding any other materials or considerable modifications of the production process but simply increasing the electrode selectivity. Graphical abstract Image 103844 [ABSTRACT FROM AUTHOR]

Quasi-solid dye-sensitized solar cells were obtained by coupling N719 dye with a cobalt gel electrolyte. Firstly, the compatibility of the liquid [Co(bpy) 3 ] 3+/2+ redox mediator with N719 was improved by modifying the surface of sensitized photoanode, which resulted in an increase in efficiency of over 100%. Most importantly, a novel room-temperature route for producing a [Co(bpy) 3 ] 3+/2+ -PMMA gel electrolyte was introduced for the first time. The formation of the gel phase was demonstrated by rheological analyses and the electrolyte was subjected to an extensive electrochemical characterization. The derived quasi-solid devices attained 70% of the efficiency of the liquid ones, and showed a degradation of only 15% after 120 days, which proved the high stability of the developed system. [ABSTRACT FROM AUTHOR]

This work deeply investigated the effect of water in terpineol-based TiO 2 screen-printing inks, commonly used for the deposition of photoanodes for dye-sensitized solar cells. The study involved all the different phases necessary for the photoanode production and the final device characterization. Firstly, inks modified with different amounts of water were produced and analyzed considering particle dispersion (DLS) and rheological behavior, while the deposited layers were analyzed in terms of morphology (FE–SEM), roughness (profilometry) transmittance (UV–Vis spectroscopy) and dye adsorption capability. Finally, the observed properties were correlated to the performance and the electrochemical behavior (EIS) of a complete DSC. The extensive study allowed to understand the real role played by the water in the ink formulation and, as a consequence, the identification of the optimal amount to be introduced in the system. Water was showed to increase the dispersion and time stability of the particle suspensions, leading to an optimized flow behavior of the inks. The ceramic films so obtained exhibited improved morphologies and enhanced optical properties and dye uptake. However, the optimal concentration for DSC application was found to be not the one that allows the best dispersability of the ceramic particles but the one that best compromised the homogeneity of the film with the highest dye uptake. This key result could not be obtained analyzing just the film morphology but necessitate a thorough analyses of all the different properties (morphological, electrochemical and photovoltaic) related to the final application. The best-performing device recorded an increase in efficiency of the 12% compared to the un-modified system. [ABSTRACT FROM AUTHOR]

In this study, a novel procedure for the production of Zr-doped TiO 2 ceramic layers, deposited by screen-printing technique, is presented. A suitable Zr precursor (Zr(IV) 2,4-pentanedionate) was added to the formulation of a standard TiO 2 ink, in order to promote the diffusion of Zr ions directly during the sintering of the deposited layers. In order to evaluate the impact of this process on the properties of the ink, thermal and rheological analysis were done; a significant effect on the flow behavior was found, related to a relevant dispersing action of the precursor. The efficacy of the method was proved by XRD analyses, that showed the stabilization of anatase phase and crystal size at high temperature (700 °C), due to Zr doping. The properties of the films were then analyzed in order to evaluate their application as photoanodes for Dye-Sensitized Solar Cells (DSCs). The use of the Zr precursor resulted to improve the film morphology, whereas it did not affect the dye adsorption capability of the TiO 2 . Electrochemical characterization pointed out increased flat band potential and density of states (DOS), the latter being potentially beneficial even for photocatalytic applications. Doped photoanodes resulted to induce a slight deterioration of the performance, pointing out the need of a more accurate optimization of the process for this application. Finally, the proposed doping method resulted effective and potentially adaptable to other dopant-semiconductor systems. [ABSTRACT FROM AUTHOR]

Abstract: A thin compact layer of TiO2 deposited on the conductive transparent substrate of a dye-sensitized solar cell photoanode, (blocking layer, BL) can enhance the performances of the entire device. In this paper, an optimized spin coating process using an alcoholic TiCl4 solution was developed and correlated to the final properties of the layer. The physicochemical characteristics of the precursor solution and the spin coating parameters were optimised to obtain a uniform layer. XRD, FE-SEM, UV–Vis spectroscopy, AFM, cyclic voltammetry and electrochemical impedance spectroscopy were used to evaluate the influence of the number of deposition cycles on the TiO2 layer. The results were compared with those obtained using a conventional dip coating technique, showing that the newly developed spin coating process produces blocking layers with superior properties. Finally, analyses of the photovoltaic performances of the complete cell confirmed that an optimized blocking layer can lead to an improvement of the solar conversion efficiency of about 84%. [Copyright &y& Elsevier]

Layered Double Hydroxides (LDH) are versatile materials that can be applied to different fields. Recently their employment in Dye-Sensitized Solar Cells (DSSCs) technology has been reported. The heart of this technology is the photoanode, a semiconductor layer sensitized with dye molecules able to absorb the sunlight. However, the traditional dye molecules are quite expensive and sensitive to thermal degradation and the sensitization process requires time and costs. The possibility to directly intercalate the dye in the LDH interlayer makes these materials very promising as innovative photoanodes. This aspect in fact would help to reduce both the time and the costs, overcome charge-transfer and recombination phenomena issues and finally increase the Photo-Conversion Efficiency (PCE) and stability. In this work, an Eosin Y-intercalated ZnAl LDH was prepared by coprecipitation and applied as photoanode material. For this purpose, a screen-printing ink was formulated and then applied onto a conductive transparent substrate. Then, complete DSSC prototypes were assembled and tested. A comparison with an analogous LDH intercalated with terephthalate and sensitized with Eosin Y showed a beneficial effect due to the presence of the dye intercalated in the structure rather than adsorbed on the surface, increasing the stability (tested for 1500 h) and efficiency of the related DSSCs. A 0.11 mA cm−2 of J SC , 568 mV of V OC and a PCE of 0.019% were obtained for the Eosin Y intercalated LDH based photoanode. Moreover, the interaction between the intercalated dye and the LDH sheets allowed to reduce charge recombination phenomena and thus to increase V OC and PCE values. • Novel one pot synthesis of an Eosin intercalated Layered Double Hydroxide (LDH) is performed. • Characterization of the material showed a total intercalation of Eosin in the LDH structure. • The LDH was applied as a Dye Sensitized Solar Cells photoanode, and tested with a solar light simulator. • Intercalating the dye rather than adsorbing it on the surface, reduced charge recombination, enhancing the DSSC efficiency. [ABSTRACT FROM AUTHOR]