Journal of the Korean Physical Society

, Volume 74, Issue 11, pp 1059–1066 | Cite as

Improvement of Quantum Efficiency and Efficiency Roll-off in OLED Devices Using Blue Thermally Activated Delayed Fluorescent Materials

  • Tae Hoon Ha
  • Eun-Hye Cho
  • Chil Won LeeEmail author
  • Hui Jae Choi
  • Oh Young Kim
  • Byung Doo ChinEmail author


The utilization of triplet excitons in the operation of organic light emitting diode play a crucial role for the enhancement of an external quantum efficiency, which will be maximized by the use of thermally activated delayed fluorescent (TADF) materials. In this study, a deep blue TADF materials with a donor-acceptor-donor structure was designed and prepared 9,9'-((2-methylpyrimidine-4,6-diyl) bis(2,1-phenylene)) bis(9H-carbazole) (DCz-mPym), (9,9' -((2- methylpyrimidine-4,6-diyl)bis(2,1-phenylene)) bis(3,6-di-tert-butyl-9H-carbazole) (DtBCz-mPym), and 5,5' -((2-methylpyrimidine-4,6-diyl) bis(2,1-phenylene)) bis (5H-benzofuro[3,2-c]carbazole) (DBFCz-mPym) using a pyrimidine as an acceptor and a carbazole derivatives as a donor. We fabricated an organic light emitting diode (OLED) using the designed three TADF materials as a dopant for light emitting layer of OLED. Correlation between the photophysical data, electrochemical properties, and the efficiency roll-off behavior were investigated for designed materials and device with appropriate structure. As a result, DBFCz-mPym, the material with very small difference between singlet energy and triplet energy, is superior to the DCz-mPym or DtBCz-mPym in terms of efficiency roll-off and harvesting of triplet excitons. Further, as a result of simulation of an efficiency roll-off curves by the increase of the current density, triple-triplet annihilation was confirmed to be the main cause.


OLED Deep-blue TADF Efficiency roll-off Triple-triplet annihilation Dihedral angle 


Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.



The present research was supported by the research fund of Dankook University in 2017. This study was supported by the Soft Chemical Materials Research Center for Organic-Inorganic Multi-Dimensional Structures, which is funded by the Gyeonggi Regional Research Center Program (GRRC Dankook 2016-B01). This research was supported by the MOTIE (Ministry of Trade, Industry & Energy (10051350) and KDRC (Korea Display Research Consortium) support program for the development of future devices technology for display industry.


  1. [1]
    L.S. Cui et al., Angew. Chem. Int. Ed. 56, 1571 (2017).CrossRefGoogle Scholar
  2. [2]
    B. W. D'Andrade and S. R. Forrest, Adv. Mater. 16, 18 (2004).Google Scholar
  3. [3]
    T. Liu et al., Adv. Func. Mater. 27, 12 (2017).Google Scholar
  4. [4]
    B. Li et al., J. Mater. Chem. C 6, 2351 (2018).Google Scholar
  5. [5]
    H. Uoyama et al., Nature 492, 234 (2012).CrossRefGoogle Scholar
  6. [6]
    Q. Zhang et al., J. Am. Chem. Soc. 134, 14706 (2012)CrossRefGoogle Scholar
  7. [7]
    O. Bezvikonnyi et al., J. Lumin. 206, 250 (2019).CrossRefGoogle Scholar
  8. [8]
    J. R. Cha, C. W. Lee, J. Y. Lee and M. S. Gong, J. Dyes Pigm. 134, 562 (2016).CrossRefGoogle Scholar
  9. [9]
    M. Regnat, K. P. Pernstich and B. Ruhstaller, Org. Electron. 70, 219 (2019)CrossRefGoogle Scholar
  10. [10]
    J. Gibson and T. J. Penfoid, Phys. Chem. Chem. Phys. 19, 8428 (2017).CrossRefGoogle Scholar
  11. [11]
    P. Rajamalli et al., J. Am. Chem. Soc. 138, 628 (2016)CrossRefGoogle Scholar
  12. [12]
    Q. Zhang et al., Dyes Pigm. 155, 51 (2018).CrossRefGoogle Scholar
  13. [13]
    G. Meng et al., Adv. Optical. Mater. 1900130 (2019).Google Scholar
  14. [14]
    Y. Xiang et al., J Mater. Chem. C. 6, 7111 (2018).Google Scholar
  15. [15]
    Y. K. Wang et al., Adv. Func. Mater. 28, 1706228 (2018).CrossRefGoogle Scholar

Copyright information

© The Korean Physical Society 2019

Authors and Affiliations

  1. 1.Department of ChemistryDankook UniversityChungcheongnam-doKorea
  2. 2.Department of Polymer Science and EngineeringDankook UniversityGyeonggi-doKorea

Personalised recommendations