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Centore R.,University of Naples Federico II | Manfredi C.,University of Naples Federico II | Fusco S.,University of Naples Federico II | Maglione C.,University of Naples Federico II | And 5 more authors.
Journal of Molecular Structure | Year: 2015

Abstract The acid-base properties of selected derivatives of the [1,2,4]triazolo[3,2-c][1,2,4]triazole fused aromatic system have been investigated by UV-vis spectroscopy. Neutral heterobicycles (HL) exhibit amphoteric behavior (they can deliver the N-H proton forming the conjugated base L- and can accept up to two protons, forming the species H2L+ and H3L++) and show an unprecedented tautomeric switching upon protonation, as revealed by single crystal X-ray analysis and confirmed by theoretical calculations. By varying the groups attached at the heterocycle, a remarkable shift of pKai values, up to 5-6 units, is observed. In particular, with strong electron attractor groups at position 7 (e.g. p-nitrophenyl or pentafluorophenyl) the neutral compounds are stronger acids than phenol or p-nitrophenol. © 2015 Elsevier B.V. All rights reserved. Source


Dessi A.,CNR Institute of Chemistry of organometallic Compounds | Dessi A.,University of Florence | Calamante M.,CNR Institute of Chemistry of organometallic Compounds | Calamante M.,University of Florence | And 12 more authors.
RSC Advances | Year: 2015

A small set of thiazolo[5,4-d]thiazole-based D-π-A organic dyes, endowed with bis-pentylpropylenedioxythiophene (ProDOT) moieties in the π-spacer, was designed with the aid of computational analysis, synthesized and characterized. The presence of bulky and electronrich ProDOT groups beside the electron poor thiazolothiazole unit induced optimal physico-chemical properties, including broad and intense visible light absorption. As a consequence, the dyes were particularly suitable for application in thin layer dye-sensitized solar cells (TiO2 thickness: 3.0-6.5 μm). Small-scale (0.25 cm2) devices prepared using standard materials and fabrication techniques gave power conversion efficiencies up to 7.71%, surpassing those obtained with two different reference dyes. Transparent larger area cells (3.6 cm2) also showed good η values up to 6.35%, not requiring the use of a co-adsorbent, and retained their initial efficiency over a period of 1000 h storage at 85 °C. These results make this new family of organic sensitizers promising candidates for successful application in the production of efficient and stable transparent DSSCs for building-integrated photovoltaics. This journal is © The Royal Society of Chemistry 2015. Source


Mastroianni S.,University of Rome Tor Vergata | Lembo A.,Dyepower Consortium | Brown T.M.,University of Rome Tor Vergata | Reale A.,University of Rome Tor Vergata | Di Carlo A.,University of Rome Tor Vergata
ChemPhysChem | Year: 2012

Mismatched or shadowed individual cells in a module can operate in the reverse bias (RB) regime. We investigate and identify key mechanisms for RB operation and degradation in dye solar cells (DSCs). Current-voltage characteristics in RB are sensitive to the type of dye utilised and to TiCl 4 substrate treatment. Subjecting the cell to a RB of 0.4 V over 740 h has little effect on conversion efficiency whereas a significant lowering is observed for the harsher stress tests at 0.6 V and by forcing a constant current equal to its I SC. For more prolonged reverse biases at I SC (>740 h), we show that depletion of [I 3 -] inside the DSC can lead the reverse bias potentials across the cells to considerably increase in time. Electrochemical impedance measurements show that the overpotentials at the counter electrodes (CEs) can eventually reach values high enough to cause hydrogen evolution. Clear evidence of gas bubbles forming inside a complete dye solar cell under reverse bias stress, leading to severe device degradation, is presented. We also show that reactions of iodine with water present in the electrolyte can play an important role in [I 3 -] depletion and in the formation of hydrogen at the Pt CE. © 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim. Source


Mastroianni S.,University of Rome Tor Vergata | Brown T.M.,University of Rome Tor Vergata | Lanuti A.,University of Rome Tor Vergata | Cina L.,University of Rome Tor Vergata | And 4 more authors.
Materials Research Society Symposium Proceedings | Year: 2012

Mismatched or shadowed individual cells in a module can operate in the Reverse Bias (RB) regime. Subjecting a dye solar cell (DSC) to an accelerated RB stress by forcing a constant current equal to 2-fold its ISC, produced significant alterations on the current-voltage (I-V) characteristics in RB with time and a severe loss of cell efficiency in 32h. We investigated and identified a key mechanism for RB charge transfer and degradation in DSCs. I-V characteristics in RB were found to be sensitive to the type of dye utilized and to TiCl4 substrate treatment. © 2012 Materials Research Society. Source


Cornaro C.,University of Rome Tor Vergata | Bartocci S.,University of Rome Tor Vergata | Musella D.,University of Rome Tor Vergata | Strati C.,University of Rome Tor Vergata | And 9 more authors.
Progress in Photovoltaics: Research and Applications | Year: 2015

New generation photovoltaic (PV) devices such as polymer and dye sensitized solar cells (DSC) have now reached a more mature stage of development, and among their various applications, building integrated PVs seems to have the most promising future, especially for DSC devices. This new generation technology has attracted an increasing interest because of its low cost due to the use of cheap printable materials and simple manufacturing techniques, easy production, and relatively high efficiency. As for the more consolidated PV technologies, DSCs need to be tested in real operating conditions and their performance compared with other PV technologies to put into evidence the real potential. This work presents the results of a 3 months outdoor monitoring activity performed on a DSC mini-panel made by the Dyepower Consortium, positioned on a south oriented vertical plane together with a double junction amorphous silicon (a-Si) device and a multi-crystalline silicon (m-Si) device at the ESTER station of the University of Rome Tor Vergata. Good performance of the DSC mini-panel has been observed for this particular configuration, where the DSC energy production compares favorably with that of a-Si and m-Si especially at high solar angles of incidence confirming the suitability of this technology for the integration into building facades. This assumption is confirmed by the energy produced per nominal watt-peak for the duration of the measurement campaign by the DSC that is 12% higher than that by a-Si and only 3% lower than that by m-Si for these operating conditions. Copyright © 2013 John Wiley & Sons, Ltd. Source

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