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120 results on '"Kulszewicz-Bajer, Irena"'

1. Thermally Controllable Tuning of Emission Properties of Phenoxazine‐Substituted Acridones as One Step Forward to Efficient Organic Light‐Emitting Diodes Based on Crystalline Emitters.

Author

Guzauskas, Matas, Volyniuk, Dmytro, Kulszewicz‐Bajer, Irena, Mahmoudi, Malek, Lazauskas, Algirdas, Jasinskas, Vidmantas, Gulbinas, Vidmantas, Pron, Adam, and Grazulevicius, Juozas V.

Subjects
ORGANIC light emitting diodes, LIGHT emitting diodes, DELAYED fluorescence, LUMINOPHORES, QUANTUM efficiency, ELECTROLUMINESCENCE
Abstract

The overwhelming majority of efficient organic light‐emitting diodes (OLEDs) are based on amorphous emitting layers. The devices with crystalline emitters usually show significantly worse performance. It is demonstrated that controlled thermal treatments of phenoxazine‐substituted acridones may lead to a spectacular improvement of photo‐ and electroluminescence of these luminophores. The three acridone derivatives studied, namely 2‐phenoxazine‐N‐hexylacridone (PHhA), 2,7‐bis‐(phenoxazine)‐N‐hexylacridone (bPHhA), and 2,7‐bis[3‐(phenoxazine)phenyl]‐N‐hexylacridone (PHPhhA), are characterized by relatively narrow photoluminescence spectra and photoluminescence quantum yields approaching 100%. These spectra can be reversibly tuned through appropriate thermal treatment of the deposited layers, undergoing shifts up to 92 nm upon transformation from amorphous to crystalline states. Strong thermally activated delayed fluorescence (TADF) observed for these compounds is manifested by a significantly higher reverse intersystem crossing rate of 1.92×106 s−1 as compared to the intersystem crossing rate of 5.68×105 s−1. These improvements are attributed to the annealing‐induced conformational equilibration due to crystallisation in combination with hosting. Adequacy of the proposed concept is demonstrated by the fabrication of devices exhibiting external quantum efficiencies reaching 20.7% – a record value for OLEDs with crystalline emitting layers. The presented approach of annealing‐induced conformational equilibration can lead to improved TADF properties for other fluorescent organic emitters presently considered inefficient. [ABSTRACT FROM AUTHOR]

Published
2023
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5. Copolymers Containing 1-Methyl-2-phenyl-imidazole Moieties as Permanent Dipole Generating Units: Synthesis, Spectroscopic, Electrochemical, and Photovoltaic Properties

Author

Kulszewicz-Bajer, Irena, primary, Nowakowski, Robert, additional, Zagórska, Małgorzata, additional, Maranda-Niedbała, Agnieszka, additional, Mech, Wojciech, additional, Wróbel, Zbigniew, additional, Drapała, Jakub, additional, Wielgus, Ireneusz, additional, and Korona, Krzysztof P., additional

Published
2022
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9. High-spin radical cations of alternating poly(m-p-anilines)

Author

Kulszewicz-Bajer, Irena, Zagorska, Malgorzata, Wielgus, Ireneusz, Pawlowski, Mariusz, Gosk, Jacek, and Twardowski, Andrzej

Subjects
Aniline -- Structure, Aniline -- Chemical properties, Polymers -- Structure, Polymers -- Chemical properties, Electrochemical analysis, Chemicals, plastics and rubber industries
Abstract

Three alternating poly(m-p-anilines) are synthesized via palladium-catalyzed amination reactions and polymers are oxidized to radical cations by the use of chemical and electrochemical methods. The presence of radical cations is demonstrated by the appearance of two bands in UV-vis spectra, the positions of which depend on chemical structure of polymers.

Published
2007

10. Molecular weight dependent charge carrier mobility in poly(3,3'-dioctyl-2,2':5',2'-terthiophene)

Author

Verilhac, Jean-Marie, Pokrop, Rafal, LeBlevennec, Gilles, Kulszewicz-Bajer, Irena, Buga, Katarzyna, Zagorska, Malgorzata, Adki, Said, and Pron, Adam

Subjects
Polymerization -- Research, Electrochemical apparatus -- Research, Charge transfer -- Research, Chemicals, plastics and rubber industries
Abstract

Poly(3,3'-dioctyl-2,2':5',2'-terthiophene) is fabricated into five fractions distinctly differing in their molecular weights in order to determine the influence of the degree of polymerization (D[P.sub.n]) on its principal physicochemical parameters. The results have shown that at least in the polythiophene family of electroactive parameters, the DP dependence of the crucial electrical parameters persists to relatively high molecular weights and have indicated the importance of the macromolecular parameters control in the fabrication of polymer-based electronic and electrochemical devices.

Published
2006

28. Triarylamine Substituted Arylene Bisimides as Solution Processable Organic Semiconductors for Field Effect Transistors. Effect of Substituent Position on Their Spectroscopic, Electrochemical, Structural, and Electrical Transport Properties

Author

Pron, Adam, primary, Reghu, Renji R., additional, Rybakiewicz, Renata, additional, Cybulski, Hubert, additional, Djurado, David, additional, Grazulevicius, Juozas V., additional, Zagorska, Malgorzata, additional, Kulszewicz-Bajer, Irena, additional, and Verilhac, Jean-Marie, additional

Published
2011
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40. VibrationalDynamics in Dendridic Oligoarylaminesby Raman Spectroscopy and Incoherent Inelastic Neutron Scattering.

Author

Kulszewicz-Bajer, Irena, Louarn, Guy, Djurado, David, Skorka, Lukasz, Szymanski, Marek, Mevellec, Jean Yves, Rols, Stephane, and Pron, Adam

Subjects
*AMINES, *VIBRATIONAL spectra, *DENDRIMERS, *INCOHERENT scattering, *NEUTRON scattering, *RAMAN spectroscopy
Abstract

Vibrational dynamics in triarylaminedendrimers was studied ina complementary way by Raman and infrared (IR) spectroscopies andincoherent inelastic neutron scattering (IINS). Three molecules wereinvestigated, namely, unsubstituted triarylamine dendrimer of thefirst generation and two dendrimers of the first and second generation,substituted in the crown with butyl groups. To facilitate the assignmentof the observed IR and Raman modes as well as the IINS peaks, vibrationalmodels, based on the general valence force field method (GVFF), werecalculated for all three compounds studied. A perfect consistencybetween the calculated and experimental results was found. Moreover,an important complementarity of the vibrational spectroscopies andIINS was established for the investigated dendrimers. The IINS peaksoriginating mainly from the C–H motions were not restrictedby particular selection rules and only dependent on the IINS crosssection. To the contrary, Raman and IR bands were imposed by the selectionrules and the local geometry of the dendrimers yielding mainly C–Cand C–N deformation modes with those of C–H nature ofmuch lower intensity. Raman spectroscopy was also applied to the studiesof the oxidation of dendrimers to their cationic forms. A strong Ramanresonance effect was observed, since the spectra of the studied compounds,registered at different levels of their oxidation, strongly dependedon the position of the excitation line with respect to their electronicspectrum. In particular, the blue (458 nm) excitation line turnedout to be insensitive toward the cationic forms yielding very limitedspectral information. To the contrary, the use of the red (647 nm)and infrared (1064 nm) excitation lines allowed for an unambiguousmonitoring of the spectral changes in dendrimers oxidized to nominallymonocationic and tricationic states. The analysis of oxidation-inducedspectral changes in the tricationic state indicated that the chargestorage configuration predominantly involved one spinless dicationof the quinoid bond sequence and one radical cation. However, smallnumbers of dications were also found in a nominally monocationic state,where only radical cations should have been present. This findingwas indicative of some inhomogeneity of the oxidation. [ABSTRACT FROM AUTHOR]

Published
2014
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