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Bucinskas A.,Kaunas University of Technology | Volyniuk D.,Kaunas University of Technology | Danyliv Y.,Kaunas University of Technology | Grazulevicius J.V.,Kaunas University of Technology | And 5 more authors.
RSC Advances

New carbazole-substituted N-annelated perylenes with different linking topologies of the chromophores were synthesized and their physical properties were studied with various experimental techniques including thermogravimetric analysis, differential scanning calorimetry, UV-vis, fluorescence and photoelectron emission spectroscopies and cyclic voltammetry. The synthesized materials exhibit extremely high thermal stability with 5% weight loss temperatures ranging from 400 to 457°C. Photoluminescence quantum yields of the solid films of the compounds range from 33 to 51%. The ionization potentials of the solid samples established by the electron photoemission technique were found to be in the range of 5.14-5.53 eV. Using the newly synthesized compounds as emissive materials, efficient organic light-emitting diodes (OLEDs) were fabricated with the emission pattern covering the broad visible region from 475 to 675 nm. Bright green OLEDs exhibited luminance exceeding 62000 cd m-2 and external quantum efficiency reaching 4.2%. © This journal is The Royal Society of Chemistry. Source

Volyniuk D.,Kaunas University of Technology | Volyniuk D.,Lviv Polytechnic | Cherpak V.,Lviv Polytechnic | Stakhira P.,Lviv Polytechnic | And 6 more authors.
Journal of Physical Chemistry C

Diphenilamino-substituted carbazoles were used as guest compounds for the preparation of highly efficient blue organic light-emitting diodes based on the phenomenon of delayed fluorescence. It was shown that the spectra of the delayed fluorescence of host-guest systems are identical to those of the prompt fluorescence and in general coincide with the photoluminescence spectra of the guest films. The congruence of the prompt and delayed fluorescence spectra is explained by the effective intermolecular triplet-singlet (T → S) energy transfer from the excited T states of the host to the S states of the guest molecules. High external electroluminescence efficiency of the fabricated electroluminescent devices, reaching 17%, is comparable to that achieved in phosphorescence-based organic light-emitting diodes. © 2013 American Chemical Society. Source

Baryshnikov G.V.,Bohdan Khmelnytsky National University | Minaev B.F.,Bohdan Khmelnytsky National University | Minaeva V.A.,Bohdan Khmelnytsky National University | Agren H.,KTH Royal Institute of Technology
Journal of Structural Chemistry

The quantum chemical DFT method with the B3LYP hybrid functional in 6-31++G(d,p) and 6-311+G(d,p) basis sets is used to calculate the equilibrium geometric parameters of different conformations of 5-(4-oxo-1,3-thiazolidine-2-ylidene)-rhodanine and its substituted form ethyl-5-(4-oxo-1,3-thiazolidine-2-ylidene)-rhodanine-3′-acetic acid applied in the synthesis of indoline and some other sensitizing dyes for solar cells. The thermodynamic parameters of four conformers and their synthesis reactions are calculated. The effect of substituents on the thermodynamic stability of the studied isomers is shown. © 2010 Pleiades Publishing, Ltd. Source

Baryshnikov G.V.,Bohdan Khmelnytsky National University | Valiev R.R.,Tomsk Polytechnic University | Karaush N.N.,Bohdan Khmelnytsky National University | Minaev B.F.,Bohdan Khmelnytsky National University | Minaev B.F.,Tomsk State University
Physical Chemistry Chemical Physics

A series of planar hetero[8]circulenes and their doubly charged ions are studied by the NICS and GIMIC methods to interpret the aromatic properties of these high symmetry species. In accordance with the performed calculations all studied hetero[8]circulenes are found to be nonaromatic compounds because paratropic and diatropic ring-currents are completely canceled yielding almost zero net current. In great contrast, the dicationic and dianionic hetero[8]circulenes demonstrate the predominant contribution of diatropic ring currents resulting in the total aromatic character of the studied doubly charged ions. This fact allows us to predict the high stability of dianionic hetero[8]circulenes and explains the extremely high stability of dicationic species observed in the mass-spectra. This journal is © the Partner Organisations 2014. Source

Baryshnikov G.V.,Bohdan Khmelnytsky National University | Minaev B.F.,Bohdan Khmelnytsky National University | Minaev B.F.,Tomsk State University | Karaush N.N.,Bohdan Khmelnytsky National University | Minaeva V.A.,Bohdan Khmelnytsky National University
RSC Advances

Novel one- and two-dimensional π-conjugated materials containing a tetraoxa[8]circulene monomer are designed on the basis of density functional theory techniques, including the periodic boundary condition for the infinite structures. These new materials are predicted to be the perspective ambipolar organic semiconductors showing a high mobility for hole and electron charge carriers. Furthermore, we demonstrate that the extension of π-conjugated tetraoxa[8]circulene units in the second dimension leads to a material with the HOMO-LUMO gap being significantly smaller than that for the 1D polymer ribbon. This fact clearly indicates the fundamental difference between the designed 1D and 2D semiconducting polymers, which constitutes the essence of modern "band-gap engineering". The consistent growth of π-conjugation determines the strong visible light absorption of the studied systems in a great contrast to the initial lack of color of the tetraoxa[8]circulene compound. The possible chemical routes to synthesize the predicted materials are discussed, including free Gibbs energy estimation for the proposed reactions. © the Partner Organisations 2014. Source

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