• Energy Research

Main DSSC components, along with their most critical materials and related issues are reviewed and feasible alternatives are envisaged.

Main DSSC components, along with their most critical materials and related issues are reviewed and feasible alternatives are envisaged.

AbstractO'Regan and Grätzel conceived a dye‐sensitized solar cell (DSSC), which operates as an artificial photosynthetic system converting solar light into electricity. Nevertheless, it is only recently that the scientific community is focusing on truly aqueous DSSCs that use water as electrolyte, thus avoiding any flammable and toxic organic solvents. The most critical aspect of these devices is the photoanode/electrolyte interface. Indeed, it is necessary to select dyes that chemisorb onto the semiconductor layer while allowing the aqueous electrolyte to thoroughly impregnate the mesostructure of the electrode; at the same time, it is necessary to avoid the anchoring unit of the dye to be hydrolyzed by water, thus causing the detachment of the sensitizer from the active material particles. This requires a thorough analysis of the structure–property relationships, in particular the evaluation of the chemical formula, stability, and performances of the dyes on the electrode surface in truly aqueous environment. Herein, we investigate nine different sensitizers, selected based on their different properties in terms of light absorption, chemical structure, and hydrophobic/hydrophilic nature. Wettability, resistance to dye desorption, and spectral variations of sensitized photoanodes, along with the photovoltaic performance of the resulting devices, are systematically investigated to identify some useful guidelines to choose and design suitable dyes of different colors for truly aqueous DSSCs.

AbstractO'Regan and Grätzel conceived a dye‐sensitized solar cell (DSSC), which operates as an artificial photosynthetic system converting solar light into electricity. Nevertheless, it is only recently that the scientific community is focusing on truly aqueous DSSCs that use water as electrolyte, thus avoiding any flammable and toxic organic solvents. The most critical aspect of these devices is the photoanode/electrolyte interface. Indeed, it is necessary to select dyes that chemisorb onto the semiconductor layer while allowing the aqueous electrolyte to thoroughly impregnate the mesostructure of the electrode; at the same time, it is necessary to avoid the anchoring unit of the dye to be hydrolyzed by water, thus causing the detachment of the sensitizer from the active material particles. This requires a thorough analysis of the structure–property relationships, in particular the evaluation of the chemical formula, stability, and performances of the dyes on the electrode surface in truly aqueous environment. Herein, we investigate nine different sensitizers, selected based on their different properties in terms of light absorption, chemical structure, and hydrophobic/hydrophilic nature. Wettability, resistance to dye desorption, and spectral variations of sensitized photoanodes, along with the photovoltaic performance of the resulting devices, are systematically investigated to identify some useful guidelines to choose and design suitable dyes of different colors for truly aqueous DSSCs.

The charge-transfer complexes have scientific relevance because this type of molecular interaction is at the basis of the activity of pharmacological compounds and because the absorption bands of the complexes can be used for the quantification of electron donor molecules. This work aims to assess the stability of the charge-transfer complexes between the electron acceptor 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) and two drugs, procaine and atenolol, in acetonitrile and ethanol. The stability of DDQ in solution and the time required to obtain the maximum complex formation were evaluated. The stoichiometry and the stability of the complexes were determined, respectively, by Job's plot method and by the elaboration of UV-vis titrations data. The latter task was carried out by using the non-linear global analysis approach to determine the equilibrium constants. This approach to data elaboration allowed us to overcome the disadvantages of the classical linear-regression method, to obtain reliable values of the association constants and to calculate the entire spectra of the complexes. NMR spectra were recorded to identify the portion of the donor molecule that was involved in the interaction. The data support the participation of the aliphatic amino groups in complex formation and exclude the involvement of the aromatic amine present in the procaine molecule.

The charge-transfer complexes have scientific relevance because this type of molecular interaction is at the basis of the activity of pharmacological compounds and because the absorption bands of the complexes can be used for the quantification of electron donor molecules. This work aims to assess the stability of the charge-transfer complexes between the electron acceptor 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) and two drugs, procaine and atenolol, in acetonitrile and ethanol. The stability of DDQ in solution and the time required to obtain the maximum complex formation were evaluated. The stoichiometry and the stability of the complexes were determined, respectively, by Job's plot method and by the elaboration of UV-vis titrations data. The latter task was carried out by using the non-linear global analysis approach to determine the equilibrium constants. This approach to data elaboration allowed us to overcome the disadvantages of the classical linear-regression method, to obtain reliable values of the association constants and to calculate the entire spectra of the complexes. NMR spectra were recorded to identify the portion of the donor molecule that was involved in the interaction. The data support the participation of the aliphatic amino groups in complex formation and exclude the involvement of the aromatic amine present in the procaine molecule.

AbstractA model photosensitizer (D5) for application in dye‐sensitized solar cells has been studied by a combination of XRD, theoretical calculations, and spectroscopic/chemometric methods. The conformational stability and flexibility of D5 and molecular interactions between adjacent molecules were characterized to obtain the driving forces that govern D5 uptake and grafting and to infer the most likely arrangement of the molecules on the surface of TiO2. A spectroscopic/chemometric approach was then used to yield information about the correlations between three variables that govern the uptake itself: D5 concentration, dispersant (chenodeoxycholic acid; CDCA) concentration, and contact time. The obtained regression model shows that large uptakes can be obtained at high D5 concentrations in the presence of CDCA with a long contact time, or in absence of CDCA if the contact time is short, which suggests how dye uptake and photovoltaic device preparation can be optimized.