1
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Chibueze CS, Visscher L. Restricted open-shell time-dependent density functional theory with perturbative spin-orbit coupling. J Chem Phys 2024; 161:094112. [PMID: 39234966 DOI: 10.1063/5.0226870] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2024] [Accepted: 08/19/2024] [Indexed: 09/06/2024] Open
Abstract
When using quantum chemical methods to study electronically excited states of open-shell molecules, it is often beneficial to start with wave functions that are spin eigenfunctions. For excited states of molecules containing heavy elements, spin-orbit coupling (SOC) is important and needs to be included as well. An efficient approach is to include SOC perturbatively on top of a restricted open-shell Kohn-Sham (ROKS) time-dependent density functional theory, which can be combined with the Tamm-Dancoff approximation (TDA) to suppress numerical instabilities. We implemented and assessed the potential of such a ROKS-TDA-SOC method, also featuring the possibility of calculating transition dipole moments between states to allow for full spectrum simulation. Our study shows that the ROKS-TDA-SOC formalism yields a clear and easy-to-use method to obtain electronically excited states of open-shell molecules that are of moderate size and contain heavy elements.
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Affiliation(s)
- Chima S Chibueze
- Department of Chemistry and Pharmaceutical Sciences, Vrije Universiteit, De Boelelaan 1108, 1081 HZ Amsterdam, The Netherlands
| | - Lucas Visscher
- Department of Chemistry and Pharmaceutical Sciences, Vrije Universiteit, De Boelelaan 1108, 1081 HZ Amsterdam, The Netherlands
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2
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Suzuki K, Kaji H. Torsion Angle Analysis of a Thermally Activated Delayed Fluorescence Emitter in an Amorphous State Using Dynamic Nuclear Polarization Enhanced Solid-State NMR. J Am Chem Soc 2023. [PMID: 37487017 DOI: 10.1021/jacs.3c05204] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/26/2023]
Abstract
The torsion angle between donor and acceptor segments of a thermally activated delayed fluorescence (TADF) molecule is one of the most critical factors in determining the performance of TADF-based organic light-emitting diodes (OLEDs) because the torsion angle affects not only the energy gap between the singlet and triplet but also the oscillator strength and spin-orbit coupling. However, the torsion angle is difficult to analyze, because organic molecules are in an amorphous state in OLEDs. Here, we determined the torsion angle of a highly efficient TADF emitter, DACT-II, in an amorphous state by dynamic nuclear polarization enhanced solid-state NMR measurements. From the experimentally obtained chemical shift principal values of 15N on carbazole, we determined the average torsion angle to be 52°. Such quantification of the torsion angles in TADF molecules in amorphous solids will provide deep insight into the TADF mechanism in amorphous OLEDs.
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Affiliation(s)
- Katsuaki Suzuki
- Institute for Chemical Research, Kyoto University, Uji, Kyoto 611-0011, Japan
| | - Hironori Kaji
- Institute for Chemical Research, Kyoto University, Uji, Kyoto 611-0011, Japan
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3
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Bhat V, Callaway CP, Risko C. Computational Approaches for Organic Semiconductors: From Chemical and Physical Understanding to Predicting New Materials. Chem Rev 2023. [PMID: 37141497 DOI: 10.1021/acs.chemrev.2c00704] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
While a complete understanding of organic semiconductor (OSC) design principles remains elusive, computational methods─ranging from techniques based in classical and quantum mechanics to more recent data-enabled models─can complement experimental observations and provide deep physicochemical insights into OSC structure-processing-property relationships, offering new capabilities for in silico OSC discovery and design. In this Review, we trace the evolution of these computational methods and their application to OSCs, beginning with early quantum-chemical methods to investigate resonance in benzene and building to recent machine-learning (ML) techniques and their application to ever more sophisticated OSC scientific and engineering challenges. Along the way, we highlight the limitations of the methods and how sophisticated physical and mathematical frameworks have been created to overcome those limitations. We illustrate applications of these methods to a range of specific challenges in OSCs derived from π-conjugated polymers and molecules, including predicting charge-carrier transport, modeling chain conformations and bulk morphology, estimating thermomechanical properties, and describing phonons and thermal transport, to name a few. Through these examples, we demonstrate how advances in computational methods accelerate the deployment of OSCsin wide-ranging technologies, such as organic photovoltaics (OPVs), organic light-emitting diodes (OLEDs), organic thermoelectrics, organic batteries, and organic (bio)sensors. We conclude by providing an outlook for the future development of computational techniques to discover and assess the properties of high-performing OSCs with greater accuracy.
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Affiliation(s)
- Vinayak Bhat
- Department of Chemistry & Center for Applied Energy Research, University of Kentucky, Lexington, Kentucky 40506-0055, United States
| | - Connor P Callaway
- Department of Chemistry & Center for Applied Energy Research, University of Kentucky, Lexington, Kentucky 40506-0055, United States
| | - Chad Risko
- Department of Chemistry & Center for Applied Energy Research, University of Kentucky, Lexington, Kentucky 40506-0055, United States
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4
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Qiu W, Liu D, Li M, Cai X, Chen Z, He Y, Liang B, Peng X, Qiao Z, Chen J, Li W, Pu J, Xie W, Wang Z, Li D, Gan Y, Jiao Y, Gu Q, Su SJ. Confining donor conformation distributions for efficient thermally activated delayed fluorescence with fast spin-flipping. Nat Commun 2023; 14:2564. [PMID: 37142564 PMCID: PMC10160101 DOI: 10.1038/s41467-023-38197-y] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2022] [Accepted: 04/19/2023] [Indexed: 05/06/2023] Open
Abstract
Fast spin-flipping is the key to exploit the triplet excitons in thermally activated delayed fluorescence based organic light-emitting diodes toward high efficiency, low efficiency roll-off and long operating lifetime. In common donor-acceptor type thermally activated delayed fluorescence molecules, the distribution of dihedral angles in the film state would have significant influence on the photo-physical properties, which are usually neglected by researches. Herein, we find that the excited state lifetimes of thermally activated delayed fluorescence emitters are subjected to conformation distributions in the host-guest system. Acridine-type flexible donors have a broad conformation distribution or bimodal distribution, in which some conformers feature large singlet-triplet energy gap, leading to long excited state lifetime. Utilization of rigid donors with steric hindrance can restrict the conformation distributions in the film to achieve degenerate singlet and triplet states, which is beneficial to efficient reverse intersystem crossing. Based on this principle, three prototype thermally activated delayed fluorescence emitters with confined conformation distributions are developed, achieving high reverse intersystem crossing rate constants greater than 106 s-1, which enable highly efficient solution-processed organic light-emitting diodes with suppressed efficiency roll-off.
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Affiliation(s)
- Weidong Qiu
- State Key Laboratory of Luminescent Materials and Devices and Institute of Polymer Optoelectronic Materials and Devices, South China University of Technology, Guangzhou, 510640, P. R. China
| | - Denghui Liu
- State Key Laboratory of Luminescent Materials and Devices and Institute of Polymer Optoelectronic Materials and Devices, South China University of Technology, Guangzhou, 510640, P. R. China
| | - Mengke Li
- State Key Laboratory of Luminescent Materials and Devices and Institute of Polymer Optoelectronic Materials and Devices, South China University of Technology, Guangzhou, 510640, P. R. China.
| | - Xinyi Cai
- State Key Laboratory of Luminescent Materials and Devices and Institute of Polymer Optoelectronic Materials and Devices, South China University of Technology, Guangzhou, 510640, P. R. China
| | - Zijian Chen
- State Key Laboratory of Luminescent Materials and Devices and Institute of Polymer Optoelectronic Materials and Devices, South China University of Technology, Guangzhou, 510640, P. R. China
| | - Yanmei He
- State Key Laboratory of Luminescent Materials and Devices and Institute of Polymer Optoelectronic Materials and Devices, South China University of Technology, Guangzhou, 510640, P. R. China
| | | | - Xiaomei Peng
- State Key Laboratory of Luminescent Materials and Devices and Institute of Polymer Optoelectronic Materials and Devices, South China University of Technology, Guangzhou, 510640, P. R. China
| | - Zhenyang Qiao
- State Key Laboratory of Luminescent Materials and Devices and Institute of Polymer Optoelectronic Materials and Devices, South China University of Technology, Guangzhou, 510640, P. R. China
| | - Jiting Chen
- State Key Laboratory of Luminescent Materials and Devices and Institute of Polymer Optoelectronic Materials and Devices, South China University of Technology, Guangzhou, 510640, P. R. China
| | - Wei Li
- State Key Laboratory of Luminescent Materials and Devices and Institute of Polymer Optoelectronic Materials and Devices, South China University of Technology, Guangzhou, 510640, P. R. China
| | - Junrong Pu
- State Key Laboratory of Luminescent Materials and Devices and Institute of Polymer Optoelectronic Materials and Devices, South China University of Technology, Guangzhou, 510640, P. R. China
| | - Wentao Xie
- State Key Laboratory of Luminescent Materials and Devices and Institute of Polymer Optoelectronic Materials and Devices, South China University of Technology, Guangzhou, 510640, P. R. China
| | - Zhiheng Wang
- State Key Laboratory of Luminescent Materials and Devices and Institute of Polymer Optoelectronic Materials and Devices, South China University of Technology, Guangzhou, 510640, P. R. China
- Ji Hua Laboratory, Foshan, 528200, P. R. China
| | - Deli Li
- State Key Laboratory of Luminescent Materials and Devices and Institute of Polymer Optoelectronic Materials and Devices, South China University of Technology, Guangzhou, 510640, P. R. China
| | - Yiyang Gan
- State Key Laboratory of Luminescent Materials and Devices and Institute of Polymer Optoelectronic Materials and Devices, South China University of Technology, Guangzhou, 510640, P. R. China
| | - Yihang Jiao
- State Key Laboratory of Luminescent Materials and Devices and Institute of Polymer Optoelectronic Materials and Devices, South China University of Technology, Guangzhou, 510640, P. R. China
| | - Qing Gu
- State Key Laboratory of Luminescent Materials and Devices and Institute of Polymer Optoelectronic Materials and Devices, South China University of Technology, Guangzhou, 510640, P. R. China
| | - Shi-Jian Su
- State Key Laboratory of Luminescent Materials and Devices and Institute of Polymer Optoelectronic Materials and Devices, South China University of Technology, Guangzhou, 510640, P. R. China.
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5
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Chaudhuri D, Patterson CH. TDDFT versus GW/BSE Methods for Prediction of Light Absorption and Emission in a TADF Emitter. J Phys Chem A 2022; 126:9627-9643. [PMID: 36515973 PMCID: PMC9806837 DOI: 10.1021/acs.jpca.2c06403] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Design concepts for organic light emitting diode (OLED) emitters, which exhibit thermally activated delayed fluorescence (TADF) and thereby achieve quantum yields exceeding 25%, depend on singlet-triplet splitting energies of order kT to allow reverse intersystem crossing at ambient temperatures. Simulation methods for these systems must be able to treat relatively large organic molecules, as well as predict their excited state energies, transition energies, singlet-triplet splittings, and absorption and emission cross sections with reasonable accuracy, in order to prove useful in the design process. Here we compare predictions of TDDFT with M06-2X and ωB97X-D exchange-correlation functionals and a GoWo@HF/BSE method for these quantities in the well-studied DPTZ-DBTO2 TADF emitter molecule. Geometry optimization is performed for ground state (GS) and lowest donor-acceptor charge transfer (CT) state for each functional. Optical absorption and emission cross sections and energies are calculated at these geometries. Relaxation energies are on the order of 0.5 eV, and the importance of obtaining excited state equilibrium geometries in predicting delayed fluorescence is demonstrated. There are clear trends in predictions of GoWo@HF/BSE, and TDDFT/ωB97X-D and M06-2X methods in which the former method favors local exciton (LE) states while the latter favors DA CT states and ωB97X-D makes intermediate predictions. GoWo@HF/BSE suffers from triplet instability for LE states but not CT states relevant for TADF. Shifts in HOMO and LUMO levels on adding a conductor-like polarizable continuum model dielectric background are used to estimate changes in excitation energies on going from the gas phase to a solvated molecule.
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6
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Kelly D, Franca LG, Stavrou K, Danos A, Monkman AP. Laplace Transform Fitting as a Tool To Uncover Distributions of Reverse Intersystem Crossing Rates in TADF Systems. J Phys Chem Lett 2022; 13:6981-6986. [PMID: 35881847 PMCID: PMC9358706 DOI: 10.1021/acs.jpclett.2c01864] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2022] [Accepted: 07/18/2022] [Indexed: 05/22/2023]
Abstract
Donor-acceptor (D-A) thermally activated delayed fluorescence (TADF) molecules are exquisitely sensitive to D-A dihedral angle. Although commonly simplified to an average value, these D-A angles nonetheless exist as distributions across the individual molecules embedded in films. The presence of these angle distributions translates to distributions in the rates of reverse intersystem crossing (krISC), observed as time dependent spectral shifts and multiexponential components in the emission decay, which are difficult to directly quantify. Here we apply inverse Laplace transform fitting of delayed fluorescence to directly reveal these distributions. Rather than a single average value, the crucial krISC rate is instead extracted as a density of rates. The modes and widths of these distributions vary with temperature, host environment, and intrinsic D-A torsional rigidity of different TADF molecules. This method gives new insights and deeper understanding of TADF host-guest interactions, as well as verifies future design strategies that target D-A bond rigidity.
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7
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Bas EE, Ulukan P, Monari A, Aviyente V, Catak S. Photophysical Properties of Benzophenone-Based TADF Emitters in Relation to Their Molecular Structure. J Phys Chem A 2022; 126:473-484. [PMID: 35061385 PMCID: PMC8895462 DOI: 10.1021/acs.jpca.1c08320] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Thermally activated delayed fluorescence (TADF) materials are commonly used in various apparatus, including organic light-emitting device-based displays, as they remarkably improve the internal quantum efficiencies. Although there is a wide range of donor-acceptor-based compounds possessing TADF properties, in this computational study, we investigated TADF and some non-TADF chromophores, containing benzophenone or its structural derivatives as the acceptor core, together with various donor moieties. Following the computational modeling of the emitters, several excited state properties, such as the absorption spectra, singlet-triplet energy gaps (ΔEST), natural transition orbitals, and the topological ΦS indices, have been computed. Along with the donor-acceptor torsion angles and spin-orbit coupling values, these descriptors have been utilized to investigate potential TADF efficiency. Our study has shown that on the one hand, our photophysical/structural descriptors and computational methodologies predict the experimental results quite well, and on the other hand, our extensive benchmark can be useful to pinpoint the most promising functionals and descriptors for the study of benzophenone-based TADF emitters.
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Affiliation(s)
- Ekin Esme Bas
- Department of Chemistry, Bogazici University, Bebek, 34342 Istanbul, Turkey
| | - Pelin Ulukan
- Department of Chemistry, Bogazici University, Bebek, 34342 Istanbul, Turkey
| | - Antonio Monari
- Université de Lorraine and CNRS, LPCT UMR 7019, F54000 Nancy, France.,Université de Paris and CNRS, ITODYS, F75006 Paris, France
| | - Viktorya Aviyente
- Department of Chemistry, Bogazici University, Bebek, 34342 Istanbul, Turkey
| | - Saron Catak
- Department of Chemistry, Bogazici University, Bebek, 34342 Istanbul, Turkey
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8
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Zhang C, Li Y, Li Z, Jiang Y, Zhang J, Zhao R, Zou J, Wang Y, Wang K, Ma C, Zhang Q. Nanofiber Architecture Engineering Implemented by Electrophoretic-Induced Self-Assembly Deposition Technology for Flash-Type Memristors. ACS APPLIED MATERIALS & INTERFACES 2022; 14:3111-3120. [PMID: 34985856 DOI: 10.1021/acsami.1c22094] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Electrophoretic deposition (EPD) has been recognized as a promising large-scale film preparation technology for industrial application. Inspired by the conventional EPD method and the crystal diffusion growth strategy, we propose a modified electrophoretic-induced self-assembly deposition (EPAD) technique to control the morphologies of organic functional materials. Here, an ionic-type dye with a conjugated skeleton and strong noncovalent interactions, celestine blue (CB), is chosen as a module molecule for EPAD investigation. As expected, CB molecules can assemble into different nanostructures, dominated by applied voltage, concentration effect, and duration. Compared to a nanopillar layered packing structure formed by the traditional spin-coating method, the EPAD approach can produce a nanofiber structure under a fixed condition of 10 V/10 min. Intriguingly, a memristor device based on a pillar-like nanostructure exhibits WORM-type behavior, while a device based on nanofibers presents Flash memory performance. The assemble process and the memory mechanism are uncovered by molecular dynamics simulations and density-functional theory (DFT) calculations. This work endows the typical EPD technique with a fresh application scenario, where an in-depth study on the growth mechanism of nanofibers and the positive effect of unique morphologies on memristor performance are offered.
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Affiliation(s)
- Cheng Zhang
- Jiangsu Key Laboratory of Micro and Nano Heat Fluid Flow Technology and Energy Application, School of Physical Science and Technology, Suzhou University of Science and Technology, Suzhou, Jiangsu 215009, China
| | - Yang Li
- Jiangsu Key Laboratory of Micro and Nano Heat Fluid Flow Technology and Energy Application, School of Physical Science and Technology, Suzhou University of Science and Technology, Suzhou, Jiangsu 215009, China
| | - Zhuang Li
- College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou 215123, China
| | - Yucheng Jiang
- Jiangsu Key Laboratory of Micro and Nano Heat Fluid Flow Technology and Energy Application, School of Physical Science and Technology, Suzhou University of Science and Technology, Suzhou, Jiangsu 215009, China
| | - Jinlei Zhang
- Jiangsu Key Laboratory of Micro and Nano Heat Fluid Flow Technology and Energy Application, School of Physical Science and Technology, Suzhou University of Science and Technology, Suzhou, Jiangsu 215009, China
| | - Run Zhao
- Jiangsu Key Laboratory of Micro and Nano Heat Fluid Flow Technology and Energy Application, School of Physical Science and Technology, Suzhou University of Science and Technology, Suzhou, Jiangsu 215009, China
| | - Jingyun Zou
- Jiangsu Key Laboratory of Micro and Nano Heat Fluid Flow Technology and Energy Application, School of Physical Science and Technology, Suzhou University of Science and Technology, Suzhou, Jiangsu 215009, China
| | - Yanan Wang
- School of Petrochemical Engineering, Changzhou University, Changzhou 213164, China
| | - Kuaibing Wang
- Jiangsu Key Laboratory of Pesticide Sciences, Department of Chemistry, College of Science, Nanjing Agricultural University, Nanjing 210095, China
| | - Chunlan Ma
- Jiangsu Key Laboratory of Micro and Nano Heat Fluid Flow Technology and Energy Application, School of Physical Science and Technology, Suzhou University of Science and Technology, Suzhou, Jiangsu 215009, China
| | - Qichun Zhang
- Department of Materials Science and Engineering, City University of Hong Kong, Kowloon, Hong Kong SAR 999077, China
- Center of Super-Diamond and Advanced Films (COSDAF), City University of Hong Kong, Kowloon, Hong Kong SAR 999077, China
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Serevičius T, Skaisgiris R, Gudeika D, Kazlauskas K, Juršėnas S. Conformational disorder enabled emission phenomena in heavily doped TADF films. Phys Chem Chem Phys 2021; 24:313-320. [PMID: 34889323 DOI: 10.1039/d1cp04905d] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Thermally activated delayed fluorescence (TADF) compounds doped in solid hosts are prone to undergo solvation effects, similar to those in the solution state. Emission peak shifts and changes in emission decay rates usually follow solid-state solvation (SSS). However, here we show that typical SSS behavior in heavily doped TADF films could be of a completely different origin, mistakenly attributed to SSS. Typically, increasing the doping load was found to redshift the emission peak wavelength and enhance the rISC rate. However, more in-depth analysis revealed that SSS actually is negligible and both phenomena are caused by the specific behavior of delayed emission. Increasing the concentration of the TADF compound was shown to enhance the concentration quenching of long-lived delayed fluorescence from conformer states with the largest singlet energy, eventually leading to a gradual redshift of the delayed emission peak wavelength. Concomitantly, the loss of long-lived delayed fluorescence entailed reverse intersystem crossing rate enhancement, though the rate-governing singlet-triplet energy gap was gradually increasing. The observed phenomena are highly unwanted, burdening molecular structure and OLED performance optimization.
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Affiliation(s)
- Tomas Serevičius
- Institute of Photonics and Nanotechnology, Vilnius University, Sauletekio 3, LT-10257 Vilnius, Lithuania.
| | - Rokas Skaisgiris
- Institute of Photonics and Nanotechnology, Vilnius University, Sauletekio 3, LT-10257 Vilnius, Lithuania.
| | - Dalius Gudeika
- Department of Polymer Chemistry and Technology, Kaunas University of Technology, Radvilenu 19, LT-50254 Kaunas, Lithuania
| | - Karolis Kazlauskas
- Institute of Photonics and Nanotechnology, Vilnius University, Sauletekio 3, LT-10257 Vilnius, Lithuania.
| | - Saulius Juršėnas
- Institute of Photonics and Nanotechnology, Vilnius University, Sauletekio 3, LT-10257 Vilnius, Lithuania.
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