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Projeto de investigação
ORGANIC REDOX MEDIATORS FOR ENERGY CONVERSION
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Electrochemical Studies of Benzoquinone, Hydrobenzoquinone, Diphenoquinone and Hydrodiphenoquinone-Based Compounds
Publication . Leitão, Flávia; Galrito, Daniel; Branco, Luís C.; Cruz, Hugo; Branco, Paula S.; DQ - Departamento de Química; Faculdade de Ciências e Tecnologia (FCT); LAQV@REQUIMTE; John Wiley and Sons Inc.
Several quinones, diphenoquinones and respective reduced forms, hydrobenzoquinones and hydrodiphenoquinones, were synthesized, and their electrochemical properties were studied by cyclic voltammetry (CV) in non-aqueous medium to assess their upcoming applicability as organic redox mediators. Benzoquinones and diphenoquinones exhibited two reversible electron transfers (ETs) as exemplified by tetra-tert-butyldiphenoquinone, which displayed ETs at standard potential (E0) at E0 = −0.53 V and E0 = −0.92 V versus SCE (saturated calomel electrode). However, hydrobenzoquinones displayed chemically irreversible ET, whereas hydrodiphenoquinones exhibited either chemically irreversible or quasi-reversible ETs. For instance, di-tert-butylhydrobenzoquinone demonstrated two irreversible ETs at Epc = 0.31 V and Epa = 1.00 V versus SCE.
Effect of Iodide-Based Organic Salts and Ionic Liquid Additives in Dye-Sensitized Solar Cell Performance
Publication . Sarrato, João; Pinto, Ana Lúcia; Cruz, Hugo; Jordão, Noémi; Malta, Gabriela; Branco, Paula S.; Lima, J. Carlos; Branco, Luís C.; LAQV@REQUIMTE; DQ - Departamento de Química; MDPI AG
The use of ionic liquid and organic salts as additives for electrolyte systems in dye-sensitized solar cells have been widely described in recent years. The tunability of their physical-chemical properties according to the cation–anion selection contributes toward their high efficiencies. For this purpose, several iodide-based organic salts including imidazolium, picolinium, guanidinium and alkylammonium cations were tested using acetonitrile/valeronitrile electrolytes and their photovoltaic parameters were compared. A best efficiency of 4.48% (4.15% for the reference) was found for 1-ethyl-2,3-dimethylimidazolium iodide ([C2DMIM]I) containing electrolyte, reaffirming the effectiveness of these additives. 4-tertbutylpyridine was included into the formulation to further improve the performance while determining which iodide salts demonstrate the highest synergy with this additive. [C2DMIM]I once again proved to be the superior additive, achieving an efficiency of 6.48% (6% for the reference). Electrochemical impedance spectroscopy was employed to elucidate the effects of the various additives, demonstrating the relevance of the counter electrode resistance on device performance. Finally, several computational descriptors for the cationic structures were calculated and correlated with the photovoltaic and resistance parameters, showing that properties related to polarity, namely relative positive charge, molecular polarizability and partition coefficient are in good agreement with the counter-electrode resistance.
Application of Covalent Organic Frameworks (COFs) as Dyes and Additives for Dye-Sensitized Solar Cells (DSSCs)
Publication . Inácio, Diogo; Pinto, Ana Lúcia; Paninho, Ana B.; Branco, Luís C.; Freitas, Sunny K. S.; Cruz, Hugo; LAQV@REQUIMTE; DQ - Departamento de Química; MDPI AG
Five Covalent Organic Frameworks (COFs) were synthesized and applied to Dye-Sensitized Solar Cells (DSSCs) as dyes and additives. These porous nanomaterials are based on cheap, abundant commercially available ionic dyes (thionin acetate RIO-43, Bismarck brown Y RIO-55 and pararosaniline hydrochloride RIO-70), and antibiotics (dapsone RIO-60) are used as building blocks. The reticular innovative organic framework RIO-60 is the most promising dye for DSSCs. It possesses a short-circuit current density (Jsc) of 1.00 mA/cm2, an open-circuit voltage (Voc) of 329 mV, a fill factor (FF) of 0.59, and a cell efficiency (η) of 0.19%. These values are higher than those previously reported for COFs in similar devices. This first approach using the RIO family provides a good perspective on its application in DSSCs as a dye or photoanode dye enhancer, helping to increase the cell’s lifespan.
Acenaphthylene-Based Chromophores for Dye-Sensitized Solar Cells
Publication . Malta, Gabriela; Pina, João; Lima, J. Carlos; Parola, A. Jorge; Branco, Paula S.; DQ - Departamento de Química; LAQV@REQUIMTE; ACS - American Chemical Society
A set of acenaphthylene dyes with arylethynyl π-bridges was tested for dye-sensitized solar cells (DSSCs). Crucial steps for the extension of the conjugated system from the acenaphylene core involved Sonogashira coupling reactions. Phenyl, thiophene, benzotriazole, and thieno-[3,2-b]thiophene moieties were employed to extend the conjugation of the π-bridges. The systems were characterized by cyclic voltammetry and by UV-vis absorption and emission. The spectroscopic characterization showed that the last three bridges resulted in red-shifted absorption and emission spectra relative to the parent phenyl-bridged compound, in accordance with TD-DFT calculations. The phenylethynyl derivative 6a achieved a conversion efficiency of 2.51% with Voc, Jsc, and FF values of 0.365 V, 13.32 mA/cm2, and 0.52, respectively. The efficiency of this compound improved to 3.15% with the addition of CDCA (10 mM), representing the best efficiency result in this study.
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Entidade financiadora
Fundação para a Ciência e a Tecnologia
Programa de financiamento
3599-PPCDT
Número da atribuição
PTDC/QUI-QOR/7450/2020