Dr. Kaspars Traskovskis Profile

Dr. Kaspars Traskovskis

at Riga Technical Univ

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Publications (10)

Proceedings Article | 30 May 2022 Poster

Carbene-metal complexes as through-space TADF emitters

Kitija Štucere, Armands Ruduss, Kaspars Traskovskis, Aivars Vembris

Proceedings Volume PC12149, PC121491F (2022) https://doi.org/10.1117/12.2621975

KEYWORDS: Temperature metrology, Quantum efficiency, Metals, Thin films, Luminescence, Copper, Chemical species, System on a chip, Scattering, Phosphorescence

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Materials for organic light-emitting diodes could be divided into several generations were last 3rd generation organic compounds exhibiting TADF which exhibit up to 100% singlet and triplet state conversation to light without the presence of heavy metal. Organometallic complexes consisting of Cu metal atom is a conceptually different class of low-cost TADF emitters. While this element does not exhibit fast room-temperature phosphorescence, it still can promote a rapid TADF, despite the considerable ΔEST gaps met in such compounds (< 0.05 eV). In this work, we present a novel approach towards TADF emitters where charge transfer through-space and metal-assisted take place. Cu complexes bearing carbazolide and carbene ligands were synthesized. Imidazole-based N-heterocyclic carbenes (NHCs) were used, with electron-accepting sulphonyl groups introduced at 4-position of the N-bound 2,6-diisopropylphenyl (Dipp) substituents. Photoluminescence bands, decays and quantum yields of complexes in various solutions, as well as PMMA-doped films with emitter concentration 5 wt%, were taken. Emission properties of thin films in the temperature diapason from 10 to 300 K were measured to estimate the charge transfer mechanism. For PL bands at room temperature excitation wavelength was either 300 or 375 nm. For temperature-induced CT emission band shifts in vacuum 345 nm excitation wavelength was used, delay 50 ns and width 10 μs. To get PL decays at room temperature a laser with a wavelength of 375 nm was used and decay was measured at the peak wavelength. For temperature-induced decays in vacuum used excitation was 345 nm, time range 50 µs. To get quantum yields at room temperature, emission and scattering ranges of the sample were measured separately with 375 nm excitation. Photoluminescence quantum yield from 0.2 to 0.3 was obtained in solutions but in thin films, it increased up to 0.9 due to the decreased torsional degree of freedom. Emission decays could be described by three exponential functions in all temperature intervals. One featuring a prompt and two delayed emission components. For both delayed emissions, the fastest and slowest emission rate decrease is observed throughout the cooling range, designating a thermally activated nature of the emissive process. The corresponding ΔEST values were estimated from Arrhenius plots and are in the range of 0.0062−0.0075 eV. By combining through-space CT architecture, giving compounds the characteristic low ΔEST values, with the presence of a heavy metal atom, which provides small, but still present SOC.

Proceedings Article | 30 May 2022 Poster

Optical and electroluminescence studies of original iridium metal complexes with aromatic staking effect

Margarita Anna Zommere, Kirills Dmitrijevs, Žanis Sisojevs, Kaspars Traskovskis, Valdis Kokars, Aivars Vembris

Proceedings Volume PC12149, PC121491E (2022) https://doi.org/10.1117/12.2621809

KEYWORDS: Organic light emitting diodes, Iridium, Metals, Luminescence, Electroluminescence, Thin films, Quantum efficiency, Glasses, Tin, Spectroscopy

Proceedings Article | 24 May 2022 Poster + Paper

Symmetrical versus asymmetrical molecular configuration in metal-assisted-through-space charge transfer TADF

Armands Ruduss, Zanis Sisojevs, Aivars Vembris, Kitija Stucere, Kaspars Traskovskis

Proceedings Volume 12149, 1214908 (2022) https://doi.org/10.1117/12.2620983

KEYWORDS: Luminescence, Organic light emitting diodes

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Proceedings Article | 24 May 2022 Poster + Paper

TADF active carbene-metal-amide complexes exhibiting through-space charge transfer: an impact of metal atom

Annija Jece, Armands Ruduss, Kitija Stucere, Aivars Vembris, Kaspars Traskovskis

Proceedings Volume 12149, 1214909 (2022) https://doi.org/10.1117/12.2621156

KEYWORDS: Chemical species, Luminescence, Gold, Phosphorescence, Copper, Molecules

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Proceedings Article | 22 May 2018 Paper

3,3'-Bicarbazole structural derivatives as charge transporting materials for use in OLED devices

Armands Ruduss, Kaspars Traskovskis, Elina Otikova, Aivars Vembris, Raitis Grzibovskis, Marcis Lielbardis, Valdis Kokars

Proceedings Volume 10687, 1068718 (2018) https://doi.org/10.1117/12.2306850

KEYWORDS: Glasses, Thin films, Absorption, Chromatography, Organic light emitting diodes, Solids, Luminescence, Silica, Molecules, OLED lighting, Fluorescence spectroscopy

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Proceedings Article | 21 May 2018 Paper

Solution-processable green phosphorescent iridium(III) complexes bearing 3,3,3-triphenylpropionic acid fragment for use in OLEDs

Kaspars Traskovskis, Aivars Vembris, Valdis Kokars

Proceedings Volume 10687, 1068715 (2018) https://doi.org/10.1117/12.2306806

KEYWORDS: Organic light emitting diodes, Molecules, Iridium, Solids, Molecular interactions, Absorption, Luminescence, Photonic integrated circuits, Quantum efficiency, Glasses

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Proceedings Article | 16 March 2015 Paper

Triphenylmethyl and triphenylsilyl based molecular glasses for photonic applications

Martins Rutkis, Kaspars Traskovskis

Proceedings Volume 9360, 93600H (2015) https://doi.org/10.1117/12.2080806

KEYWORDS: Chromophores, Nonlinear optics, Glasses, Molecular photonics, Silicon, Molecules, Thin films, Photonic glasses, Solids, Bromine

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Proceedings Article | 22 October 2014 Paper

Recording and self-enhancement of dynamic polarization gratings in degenerate four-wave-mixing geometry

A. Ozols, A. Belyaev, V. Kokars, P. Augustovs, K. Traskovskis, D. Saharov

Proceedings Volume 9421, 942108 (2014) https://doi.org/10.1117/12.2084046

KEYWORDS: Polarization, Holography, Photodetectors, Chalcogenides, Holograms, Two wave mixing, Reflection, Image transmission, Mirrors, Glasses

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Proceedings Article | 16 May 2012 Paper

An improved molecular design of obtaining NLO active molecular glasses using triphenyl moieties as amorphous phase formation enhancers

Kaspars Traskovskis, Igors Mihailovs, Andrejs Tokmakovs, Valdis Kokars, Martins Rutkis

Proceedings Volume 8434, 84341P (2012) https://doi.org/10.1117/12.922391

KEYWORDS: Chromophores, Nonlinear optics, Glasses, Absorption, Bridges, Molecular bridges, Solids, Refractive index, Molecules, Carbon

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Proceedings Article | 8 September 2011 Paper

Synthesis and nonlinear optical properties of novel N,N-dihydroxyethyl-based molecular organic glasses using triaryl substitutes as amorphous phase formation enhancers

Kaspars Traskovskis, Igors Mihailovs, Andrejs Tokmakovs, Valdis Kokars, Valdis Kampars, Martins Rutkis

Proceedings Volume 8113, 81130Z (2011) https://doi.org/10.1117/12.893381

KEYWORDS: Nonlinear optics, Glasses, Chromophores, Crystals, Structural design, Molecules, Spectroscopy, Thin films, Harmonic generation, Electro optics

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Showing 5 of 10 publications

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