1,721,014 research outputs found
Heteroaromatic-based organic and organometallic dyes for dye-sensitized solar cells
No full textSolar energy is the most abundant clean and renewable energy source but
photovoltaic technology has not yet found widespread use due to its high intrinsic
costs. Emerging thin-film molecular-based photovoltaic technologies, based on
organic and organometallic molecules and polymers, offer a unique promise of
cheap, efficient, and robust devices. Amongst the new technologies, dye-sensitized
solar cells (DSCs) show one of the best potential of high-conversion efficiency and
low-cost manufacturing.
Here we present our recent studies on DSC based on organic and organometallic
photosensitizers. The organic sensitizers have an unprecedented multi-branched
structure, at variance with the conventional uni-dimensional geometry, for
enhanced power conversion efficiencies and stabilities. We also report our most
recent studies on a new family of cyclometalated complexes for efficient and more
stable devices. In both cases the design of the sensitizer dyes originated from a
careful selection of electron-rich and electron-poor aromatic and heteroaromatic
fragments in order to tune, and optimize, optical and energetic properties and, in
turn, device performance. The new dyes have been completely characterized in
their optical and electrochemical properties and investigated in photovoltaic
devices. [1]
[1] A. Abbotto, F. Sauvage, C. Barolo, F. De Angelis, S. Fantacci, M. Graetzel, N.
Manfredi, C. Marinzi, M. K. Nazeeruddin, Dalton Trans. 2011, 40, 234-242; A.
Abbotto, N. Manfredi, C. Marinzi, F. D. Angelis, E. Mosconi, J. -H. Yum, Z.
Xianxi, M. K. Nazeeruddin, M. Gratzel, Energy Environ. Sci. 2009, 2, 1094-1101;
A. Abbotto, C. Barolo, L. Bellotto, F. D. Angelis, M. Gratzel, N. Manfredi, C.
Marinzi, S. Fantacci, J. -H. Yum, M. K. Nazeeruddin, Chem. Commun. 2008, 42,
5318-5320
A spectroscopic and magnetic study of complexes of bis(2-benzothiazolyl)methanate and bis(2-benzoxazolyl) methanate with Co(II), Ni(II), Cu(II) and Zn(II)
No full textThe co-ordination geometry of the complexes M(bbtm)2 and M(bbom)2 (M: Co, Ni, Cu, Zn; bbtm, bis(2-benzothiazolyl)methanate; bbom, bis(2-benzoxazolyl)methanate) are discussed on the basis of their IR, Raman, resonance Raman, electronic and ESR spectra. Compounds of Ni, Co, Zn with both ligands and Cu(bbom)2/ resulted to have a distorted tetrahedral geometry. The distortion towards a square planar geometry is more marked for the M(bbtm)2 series than for the M(bbom)2 one. It has been impossible to suggest a co-ordination geometry for Cu(bbtm)2, that probably has a polymeric structure
Rationalizing the electronic properties of two classes of push–pull DSSC sensitizers based on Zn(II) di- or tetrarylporphyrinates substituted in meso or beta-pyrrolic positions: an electrochemical investigation
No full textPush–pull Zn(II)-porphyrinates have recently shown attracting performances as
light harvesting systems in dye-sensitized solar cells (DSSCs). To fully exploit their
intrinsically high efficiency it is important to finely tune their HOMO and LUMO levels,
which can be achieved by proper choice of the push and pull substituents. Of course
such target-oriented molecular design requires the availability of reliable relationships
between molecular structure and electronic properties; therefore we have carried out
a detailed electrochemical investigation, also supported by spectroscopy and
theoretical computations, on a wide, systematic range of Zn(II)-porphyrinates:
(a) a family of 5,15-meso substituted ones with phenylethynyl linkers, including a
first "benchmark" symmetric series carrying on the opposite terminals the same
substituent (N(CH3)2, OCH3, COOCH3, COOH, NO2); and a second push–pull one,
with the terminal positions carrying one donor and one acceptor group belonging to
the series above. Moreover, two suitably modified porphyrins allowed evaluation of
the effects of (i) the presence or absence of the phenyl group in the linker between
the porphyrin core and the acceptor group, and (ii) the effect of perfluorination on the
same phenyl group;
(b) a family of mono and, for the first time, disubstituted push-pull ZnIIporphyrinates
bearing a variety of ethynyl-phenyl moieties in β-pyrrolic position,
which were compared with their meso analogues, producing evidence that, although
the HOMO-LUMO energy gap of the meso substituted push-pull dyes is lower, the β
mono or disubstituted push-pull porphyrinic dyes show comparable or better
efficiencies when acting as sensitizers in DSSCs, possibly on account of a more
facile charge injection into TiO2.
A rationalization scheme is proposed concerning relationship between structure
and redox properties, affording inter alia interesting clues on the different localization
of the redox centres and the effective conjugation between the porphyrin core and
the side chains as a function of the molecular design.
References:
[1] P. R. Mussini, A. Orbelli Biroli, F. Tessore, M. Pizzotti, C. Biaggic, G. Di Carlo, M.
G. Lobello, F. De Angelis, Electrochimica Acta 85 (2012) 509– 523
[2] G. Di Carlo, A. Orbelli Biroli, M. Pizzotti, F. Tessore, V. Trifiletti, R. Ruffo, A.
Abbotto, A. Amat, F. De Angelis, P. R. Mussini, Chemistry-a European Journal, in
press (2013)
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Poling under swelling conditions of cross-linked polymer networks as a novel alignment procedure for covalently attached NLO chromophores.
No full textHybrid organic-inorganic sol-gel materials for second order non-linear optical and laser applications based on highly efficient heterocycle-based push-pull systems
No full textMaterials and Devices for Photonic Circuits, SPIE vol. 380
Novel Heteroaromatic and Heteroalicyclic Metal Methanates, [ML2] {L = bis(2-Benzothiazolyl) and bis[2-(delta2-Thiazolinyl)]}
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