Home / The University / Faculties / Faculty of Chemistry and Pharmacy / Structures / Departments / Physical Chemistry / Laboratory of Quantum and Computational Chemistry / Development of efficient OLED emitters by directed tuning of excited states

   

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Dissemination of results

 

Project overview

Over the past few decades, technologies have been advancing at incredible speed, becoming more complex and innovative. A branch is dedicated to the development of light emitting devices. Among them, one of the technologies undergoing the most intense market development at present is that devoted to the production of light emitting diodes (LEDs) [J. Cho, J. H. Park, J. K. Kim, E. F. Schubert, Laser Photon. Rev. 2017, 11, 1600147]. In order to meet the demand for better and more efficient materials compared to the currently used LEDs, extensive research in the field of electronics and mechatronics is continuously undertaken. More and more materials based on organic compounds are being created. Our study is devoted to the optimization of the properties of light emitting substances, the so-called light emitters, to be used in new more efficient and cost-effective OLEDs (organic light emitting diodes). OLEDs are applied widely in different light emitting components – lamps, automobile parts, displays of electronic devices, etc. Their advantages are low energy consumption, fast reaction times, wide viewing angles, flexibility and plasticity allowing production in various forms [J-X. Chen, W-W. Tao, K. Wang, C-J. Zheng, W. Liu, X. Li, X-M. Ou, X-H. Zhang, Org. Electron. 2018, 57, 327].

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However, OLED-based devices suffer from one major drawback - a relatively short lifespan of blue light emitting diodes due to instability [C. Y. Tu, W. Z. Liang, Org. Electron. 2018, 57, 74]. Hence, the main goal of the current project is to develop new blue light emitting materials through directed molecular design, synthesis and instrumental characterization. They should have improved characteristics and could be applied in OLEDs, yielding higher efficiency.

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The studied compounds are small π-conjugated organic molecules based on a molecular framework donor-bridge-acceptor obtained in previous studies [G. Valchanov, A. Ivanova, A. Tadjer, D. Chercka, M. Baumgarten Org. Electron. 2013, 14, 2727; G. Valchanov, A. Ivanova, A. Tadjer, D. Chercka, M. Baumgarten J. Phys. Chem. А 2016, 120, 6944]. The emitters are going to be optimized within the project so that they could effectively emit blue light due to thermally activated delayed fluorescence (TADF) [Q. Wei, Z. Ge, Macromol. Rapid Commun. 2019, 40, 1800570].

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The studies will be conducted by combining quantum chemical (DFT) calculations, synthetic and spectroscopic techniques, to clarify the mechanism of the TADF process and to enhance the efficiency of the TADF emission in the blue spectrum. During the project, DFT calculations, modern methods of organic synthesis and steady-state and time-resolved absorption and emission measurements will be applied in a coordinated manner to ensure comprehensiveness of the description. The most prospective compounds, provided by the modeling, will be synthesized and experimentally characterized. At the same time, the collected experimental data will be used to validate and develop the modeling procedures. The final outcome of the project will be organic blue light emitters with improved characteristics and more in-depth understanding of the TADF process therein.

 

Objectives of the project

  • Up to 100 % internal quantum efficiency upon composition of organic compounds, utilizing successfully the process of thermally activated delayed fluorescence (TADF);
  • Directed design, synthesis and characterization of organic emitters based on the TADF process and their inclusion in organic light emitting devices with high emission intensity;
  • Checking the applicability of various DFT functionals and basis sets for optimization of the structure and optical features of the molecules;
  • Synthesis of the proposed TADF emitters with high purity;
  • Experimental determination of the basic photophysical properties of the synthesized compounds;
  • Evaluation of the dynamic characteristics of the processes;
  • Comparative analysis of calculated and experimentally determined TADF parameters.