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2. Rubbing induced reversible fluorescence switching in thiophene-based organic semiconductor films by mechanical amorphisation

Author

Cavallini M., Manet I., Brucale M., Favaretto L., Melucci M., Maini L., Liscio F., Della Ciana M., Gentili D., Cavallini M., Manet I., Brucale M., Favaretto L., Melucci M., Maini L., Liscio F., Della Ciana M., and Gentili D.

Subjects
integumentary system, polymorph, organic semiconductor, mechanical transformation
Abstract

Here, we applied rubbing on thiophene-basedorganic semiconductor thin films to induce a reversible mechanical amorphisation. Amorphisation is associated with fluorescence switching, which is regulated by the polymorphic nature of the film. Thermal annealing of rubbed films produces an opposite effect with respect to rubbing, inducing film crystallization. Notably, thermal crystallisation starts at a low temperature but generates the polymorph stable at a high temperature in the bulk. The mechanism of mechanical transformation is explained considering the mechanical properties of the material and demonstrated through combined X-ray diffraction, atomic force microscopy and photoluminescence at confocal microscopy. This journal is

Published
2021

3. Oligothiophene S,S-dioxides. Synthesis and electronic properties in relation to the parent oligothiophenes

Author

Barbarella, G., Favaretto, L., Sotgiu, G., Zambianchi, M., Antolini, L., Pudova, O., and Bongini, A.

Subjects
Bromine -- Research, Oxidation-reduction reaction -- Research, Organic compounds -- Synthesis, Biological sciences, Chemistry
Abstract

A study was conducted to demonstrate that the coupling of brominated thiophene S,S-dioxides with thienyl stannanes in the presence of a palladium-catalyst enables easy and selective insertion of thiophene S,S-dioxide moieties into the skeleton of bi-, ter-, quarter- and quinquethiophenes. This allows the achievement of continuous modulation of the electronic and redox properties of the system. Results revealed that it is possible to shift from easily oxidized oligothiophenes to easily reduced oligothiophene S,S-dioxides containing alternating aromatic and nonaromatic moieties.

Published
1998

16. Interplay between stimulated emission and singlet-singlet annihilation in oligothiophene dioxide thin films.

Author

Lattante, S., De Giorgi, M., Barbarella, G., Favaretto, L., Gigli, G., Cingolani, R., and Anni, M.

Subjects
THIN films, SURFACES (Technology), LIGHT emitting diodes, SEMICONDUCTOR diodes, FIELD-effect transistors, PHOTOLUMINESCENCE
Abstract

We have studied the optical properties of different thienyl-S,S-dioxide oligothiophenes under strong excitation. No stimulated emission is observed in neat films due to singlet-singlet bimolecular annihilation. The bimolecular recombination constant is quantified from a rate equation model in the limit of constant annihilation rate. We demonstrate that tunable stimulated emission in the range 490–660 nm, due to optical gain with an estimated cross section of the order of σg≈10-17 cm2, can be obtained by blending the active molecule with small quantities of inert polycarbonate poly(bisphenol-A-carbonate) (PC). The presence of amplified spontaneous emission (ASE) for a PC:active molecule relative concentration as small as 1:500 suggests that the polycarbonate role is to reduce the intermolecular diffusion rate rather than to isolate the active molecules. Moreover, for higher PC content, a continuous decrease of the bimolecular quenching role is observed. These results demonstrate that the absence of stimulated emission in neat films is not necessarily due to intrinsic molecular properties, as strong ASE can be obtained by slightly modifying the molecule interaction during the deposition process. This approach could allow a considerable extension of the number of molecules showing stimulated emission for organic laser applications. [ABSTRACT FROM AUTHOR]

Published
2006
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17. The effects of oxygenation on the optical properties of dimethyl-dithienothiophenes: Comparison between experiments and first-principles calculations.

Author

Raganato, M. F., Vitale, V., Sala, F. Della, Anni, M., Cingolani, R., Gigli, G., Favaretto, L., Barbarella, G., Weimer, M., and Görling, A.

Subjects
RESEARCH, CONSTITUTION of matter, PHOTOLUMINESCENCE, SPECTRUM analysis, ABSORPTION, THEORY, EMISSIONS (Air pollution)
Abstract

Modifications of the optical properties of dimethyl-dithienothiophenes due to the oxygen functionalization of the central sulfur atom are investigated. We have measured the absorption, photoluminescence (PL) and PL excitation spectra, the PL quantum efficiencies, and the PL decay times. These experimental results are interpreted and compared with first-principles time-dependent density-functional theory calculations, which predict, for the considered systems, excitation and emission energies with an accuracy of 0.1 eV. It is found that the oxygenation strongly changes optical and photophysical properties. These effects are related to the modifications of the energetically lowest-unoccupied molecular orbital and the energetically second highest occupied one, which change the relative position of the two lowest singlet and triplet excited states. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Published
2004
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18. Nonradiative relaxation in thiophene-S,S-dioxide derivatives: The role of the environment

Author

Anni, M., Cingolani, R., Sala, F. Della, Gigli, G., Raganato, M.F., Barbarella, G., Fabiano, E., Favaretto, L., Lattante, S., and Gorling, A.

Subjects
Sulfur dioxide -- Research, Thiophene -- Chemical properties, Chemicals, plastics and rubber industries
Abstract

The intramolecular radiative and nonradiative relaxation processes of three thiophene-S,S-dioxide derivatives with different molecular rigidity are investigated in different solutions and inert matrix. It is shown that the fluorescence quantum efficiency and the relaxation dynamics are strongly dependent on the environment viscosity, whereas they are almost independent of the environment polarity.

Published
2005

19. Synthesis and investigation on processing-depending polarized fluorescence emission in thin-films of 2,2′-([2,2′-bithiophene]-5,5′-diyl)bis(5-octyl-4-phenyl-4H-thieno[2,3-c]pyrrol-6(5H)-one)

Author

Favaretto, L., primary, Zambianchi, M., additional, Lopez, S. G., additional, Mazzanti, A., additional, Zanardi, C., additional, Seeber, R., additional, Gentili, D., additional, Valle, F., additional, Benvenuti, E., additional, Muccini, M., additional, Ruani, G., additional, Mercuri, F., additional, Milita, S., additional, Liscio, F., additional, Cavallini, M., additional, Toffanin, S., additional, and Melucci, M., additional

Published
2017
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23. ORGANIC SEMICONDUCTOR MATERIAL

Author

Melucci, M, Favaretto, L, Zambianche, M, Capelli, R, and Muccini, M

Subjects
molecular design, organic semiconductor, organic light emitting transistors
Published
2012

25. Self-Complementary Nucleoside-Thiophene Hybrid Systems: Synthesis and Supramolecular Organization

Author

Navacchia, ML (Navacchia, Maria Luisa), Favaretto, L (Favaretto, Laura), Treossi, E (Treossi, Emanuele), Palermo, V (Palermo, Vincenzo), and Barbarella, G (Barbarella, Giovanna)

Subjects
synthesis, thin films, conjugated polymers, radical polymerization, self-organization
Abstract

Versatile synthetic methods towards a variety of thiophene-nucleobase hybrid systems are reported. Adenine- and thymine-based modified nucleosides characterized by a bithiophene unit linked to the C5' or C8 position through an ethylenamino or an ethylensulfanyl bridge were synthesized and successfully polymerized in the presence of FeCl3. The self-organization properties of the pure polymers as well as their mixtures - with complementary nucleobases - were investigated by means of optical microscopy and AFM in cast film showing complex supramolecular structures resulting from the interplay of multiple intermolecular interactions.

Published
2010

26. Bicolor Electroluminescent Pixels from Single Active Molecular Material

Author

Viola I., Piliego C., Favaretto L., Barbarella G., Cingolani R., and Gigli G.

Subjects
LIGHT-EMITTING-DIODES, PHOTOLITHOGRAPHY, THIOPHENE, CONJUGATED POLYMERS
Abstract

We report on the fabrication of the first bicolor micropixelated OLED from a single molecular material using a single-step bottom up procedure, The implementation of a deposition technique, based on a spatial-switch and con formational-sensitive STD surface-tension-driven lithography, has allowed us to exploit the spontaneous supramolecular properties and the conformational flexibility of a conjugated thiophene-based material, 6-bis-(50-hexyl-[2, 20]bithiophen-5-yl)-3, 5-dimethyl-dithieno[3, 2-b: 20, 30-d]-thiophene (DTT7Me). The existence of two regularly alternating emitting regions on a micrometer scale allows obtaining electroluminescent emission at two different wavelengths from a single material.

Published
2010

28. Rigid-Core Oligothiophene-S,S-dioxides with High Photoluminescence Efficiencies both in Solution and in the Solid State

Author

Barbarella G., Favaretto L., Sotgiu G., Antolini L., Gigli G., Cingolani R., and Bongini A.

Subjects
optical properties, quantum efficiency, oligothiophenes
Abstract

The photoluminescence (PL) frequencies and quantum efficiencies of dithieno[3,2-b;2',3'-d]thiophene-4,4-dioxide (1), its 3,5-dimethyl derivative (2), and the corresponding 4-oxide (3) are reported and discussed in relation to their single-crystal X-ray structures. The peculiar packing modalities of dioxides 1 and 2, based on dimeric units originated by short S . . .O contacts between molecules related by an inversion center, cause an unusually high bathocromic shift of PL frequencies from solution to solid state. This effect is accompanied by a marked decrease in solid-state PL efficiencies (12% and 16%) compared to those in solution (75% and 77%). In monoxide 3 the loss of local symmetry inherent to the change SO2 --> SO deeply modifies the self-assembly and PL properties, and the PL efficiency in the solid state is close to that in solution. Ab initio calculations on the ground and excited states of compound 1 were performed and compared to those of a conformationally mobile counterpart. Oligomers containing dithienothiophene 2 as internal core were synthesized and found to be characterized by high PL efficiencies in the solid-state (up to 48%) as well as in solution (up to 85%). The current-voltage and luminance-voltage plots of an electroluminescent diode fabricated with one of these new rigid-core oligothiophene-S,S-dioxides are reported.

Published
2001

33. Thienopyrrolyl dione end-capped oligothiophene ambipolar semiconductors for thin film- and light emitting transistors

Author

Melucci M., Zambianchi M., Favaretto L., Gazzano M., Zanelli A., Monari, Capelli R., Troisi S., Toffanin S., Muccini M., M. Melucci, M. Zambianchi, L. Favaretto, M. Gazzano, A. Zanelli, M. Monari, R. Capelli, S. Troisi, S. Toffanin, and M. Muccini

Subjects
Materials science, Band gap, 02 engineering and technology, 010402 general chemistry, 01 natural sciences, Catalysis, law.invention, law, Materials Chemistry, Thin film, HOMO/LUMO, thienopyridine derivative, THIN FILM, organic semiconductor, business.industry, Ambipolar diffusion, Transistor, Metals and Alloys, organic devices, General Chemistry, 021001 nanoscience & nanotechnology, 0104 chemical sciences, Surfaces, Coatings and Films, Electronic, Optical and Magnetic Materials, organic materials, Semiconductor, Ceramics and Composites, Optoelectronics, 0210 nano-technology, business
Abstract

The design, synthesis and structure-property investigation of a new thienopyrrolyl dione substituted oligothiophene material showing reduced band gap energy, low lying LUMO energy level and ambipolar semiconducting behaviour is described.

Published
2011

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