Organic light-emitting diodes with new dyes based on coumarin

The results of studying the luminescent properties of organic light-emitting diodes based on new luminescent compounds containing a coumarin fragment are presented. The light-emitting diodes were fabricated by spin-coating and thermal evaporation in an argon atmosphere in a clean room. Measurements of the LED characteristics were carried out by optical spectroscopy, as well as by electrical methods. It has been experimentally shown that deposition of an OLED active layer based on luminescent compounds containing a coumarin core can lead to the formation of dimers, the luminescence spectra of which differ significantly from the corresponding spectra of the original materials in toluene. A variation in the structure of the compound leads to a change in both the current-voltage characteristics of the resulting device and the luminescence spectra. These changes appeared due to the difference in the electronic structure of these materials as well as due to different values of charge carrier mobilities and the potential barriers at the heterointerface with other OLED layers. The results obtained may serve as the basis for systematizing knowledge about the dependence of the properties of new luminescent materials, which include a coumarin core, on their structure. The developed structures can become prototypes for industrially produced light-emitting devices that specifically emit white light.

1. Luo J., Rong X.F., Ye Y.Y., Li W.Z., Wang X.-Q., Wang W. Research progress on triarylmethyl radical-based high-efficiency OLED. Molecules, 2022, vol. 27, no. 5, pp. 1632. https://doi.org/10.3390/molecules27051632

2. Corrêa Santos D., Vieira Marques M.F. Blue light polymeric emitters for the development of OLED devices. Journal of Materials Science: Materials in Electronics, 2022, vol. 33, no. 16, pp. 12529–12565. https://doi.org/10.1007/s10854-022-08333-3

3. Palomaki P. Quantum Dots + OLED = Your Next TV: Formerly rival technologies will come together in new Samsung displays. IEEE Spectrum, 2022, vol. 59, no. 1, pp. 52–53. https://doi.org/10.1109/MSPEC.2022.9676350

4. Lee S., Hahm D., Yoon S.Y., Yang H., Bae W.K., Kwak J. Quantumdot and organic hybrid light-emitting diodes employing a blue common layer for simple fabrication of full-color displays. Nano Research, 2022, vol. 15, no. 7, pp. 6477–6482. https://doi.org/10.1007/s12274-022-4204-y

5. Vashchenko A.A., Vitukhnovskii A.G., Lebedev V.S., Selyukov A.S., Vasiliev R.B., Sokolikova M.S. Organic light-emitting diode with an emitter based on a planar layer of CdSe semiconductor nanoplatelets. JETP Letters, 2014, vol. 100, no. 2, pp. 86–90. https://doi.org/10.1134/S0021364014140124

6. Selyukov A.S., Vitukhnovskiia A.G., Lebedev V.S., Vashchenko A.A., Vasiliev R.B., Sokolikova M.S. Electroluminescence of colloidal quasi-two-dimensional semiconducting CdSe nanostructures in a hybrid light-emitting diode. Journal of Experimental and Theoretical Physics, 2015, vol. 120, no. 4, pp. 595–606. https://doi.org/10.1134/S1063776115040238

7. Eliseeva S.V., Bünzli J.C.G. Rare earths: jewels for functional materials of the future. New Journal of Chemistry, 2011, vol. 35, no. 6, pp. 1165–1176. https://doi.org/10.1039/C0NJ00969E

8. Eliseeva S.V., Bünzli J.C.G. Lanthanide luminescence for functional materials and bio-sciences. Chemical Society Reviews, 2010, vol. 39, no. 1, pp. 189–227. https://doi.org/10.1039/B905604C

9. Liang A., Ying L., Huang F. Recent progresses of iridium complexcontaining macromolecules for solution-processed organic lightemitting diodes. Journal of Inorganic and Organometallic Polymers and Materials, 2014, vol. 24, no. 6, pp. 905–926. https://doi.org/10.1007/s10904-014-0099-8

10. Wei Q., Fei N., Islam A., Lei T., Hong L., Peng R., Fan X., Chen L., Gao P., Ge Z. Small-molecule emitters with high quantum efficiency: mechanisms, structures, and applications in OLED devices. Advanced Optical Materials, 2018, vol. 6, no. 20, pp. 1800512. https://doi.org/10.1002/adom.201800512

11. Jin J., Zhu Z., Yan J., Zhou X., Cao C., Chou P.-T., Zhang Y.-X., Zheng Z., Lee C.-S., Chi Y. Iridium (III) phosphors–bearing functional 9-phenyl-7, 9-dihydro-8h-purin-8-ylidene chelates and bluehyperphosphorescent OLED devices. Advanced Photonics Research, 2022, vol. 3, no. 7, pp. 2100381. https://doi.org/10.1002/adpr.202100381

12. Chen J.X., Liu W., Zheng C.J., Wang K., Liang K., Shi Y.-Z., Ou X.-M., Zhang X.-H. Coumarin-based thermally activated delayed fluorescence emitters with high external quantum efficiency and low efficiency roll-off in the devices. ACS Applied Materials & Interfaces, 2017, vol. 9, no. 10, pp. 8848–8854. https://doi.org/10.1021/acsami.6b15816

13. Traven V.F., Cheptsov D.A. Sensory effects of fluorescent organic dyes. Russian Chemical Reviews, 2020, vol. 89, no. 7, pp. 713. https://doi.org/10.1070/RCR4909

14. Huang D., Chen Y., Zhao J. Access to a large stokes shift in functionalized fused coumarin derivatives by increasing the geometry relaxation upon photoexcitation: An experimental and theoretical study. Dyes and Pigments, 2012, vol. 95, no. 3, pp. 732–742. https://doi.org/10.1016/j.dyepig.2012.04.024

15. Drexhage K.H. Dye Lasers. Springer-Verlag, 1973, 285 p.

16. Yin Y., Lü Z., Deng Z., Liu B., Mamytbekov Z.K., Hu B. White-lightemitting organic electroluminescent devices with poly-TPD as emitting layer. Journal of Materials Science: Materials in Electronics, 2017, vol. 28, no. 24, pp. 19148–19154. https://doi.org/10.1007/s10854-017-7871-9

17. Kotchapradist P., Prachumrak N., Sunonnam T., Tarsang R., Namuangruk S., Sudyoadsuk T., Keawin T., Jungsuttiwong S., Promarak V. N-coumarin derivatives as hole-transporting emitters for high efficiency solution-processed pure green electroluminescent devices. Dyes and Pigments, 2015, vol. 112, pp. 227–235. https://doi.org/10.1016/j.dyepig.2014.06.032

18. Sahoo R.K., Atta S., Singh N.D., Jacob C. Influence of functional derivatives of an amino-coumarin/MWCNT composite organic hetero-junction on the photovoltaic characteristics. Materials Science in Semiconductor Processing, 2014, vol. 25, pp. 279–285. https://doi.org/10.1016/j.mssp.2014.01.001

19. Yadav R.A.K., Dubey D.K., Chen S.Z., Liang T.W., Jou J-H. Role of molecular orbital energy levels in OLED performance. Scientific Reports, 2020, vol. 10, no. 1, pp. 9915. https://doi.org/10.1038/s41598-020-66946-2