Asymmetric Host Molecule Bearing Pyridine Core for Highly Efficient Blue Thermally Activated Delayed Fluorescence OLEDs

Jiwon Yoon, Seong Keun Kim, Hyung Jong Kim, Suna Choi, Sang Won Jung, Hyuna Lee, Jun Yun Kim, Dae Wi Yoon, Chang Wook Han, Weon Sik Chae, Jang Hyuk Kwon, Min Ju Cho, Dong Hoon Choi

Research output: Contribution to journalArticlepeer-review

2 Citations (Scopus)

Abstract

In this study, two host materials, pCzBzbCz and pCzPybCz, are synthesized to achieve a high efficiency and long lifetime of blue thermally activated delayed fluorescence organic light-emitting diodes (TADF-OLEDs). The molecular design strategy involves the introduction of a pyridine group into the core structure of pCzPybCz as an electron-withdrawing unit, and an electron-donating phenyl group into the structure of pCzBzbCz. These host materials demonstrate good thermal stability and high triplet energy (T1=3.07 eV for pCzBzbCz and 3.06 eV for pCzPybCz) for the fabrication of blue TADF-OLEDs. In particular, pCzPybCz-based OLED devices demonstrate an external quantum efficiency (EQE) of 22.7 % and an operational lifetime of 24 h (LT90, time to attain 90 % of initial luminance) at an initial luminance of 1000 cd m−2. This superior lifetime could be explained by the C−N bond dissociation energy (BDE) in the host molecular structure. Furthermore, a mixed-host system using the electron-deficient 2,4-bis(dibenzo[b,d]furan-2-yl)-6-phenyl-1,3,5-triazine (DDBFT) is proposed to inhibit the formation of the anion state of our host materials. In short, the device operational lifetime is further improved by applying DDBFT. The carbazole-based asymmetric host molecule containing a pyridine core realizes a high-efficiency blue TADF-OLED showing a positive effect on the operating lifetime, and can provide useful strategies for designing new host materials.

Original languageEnglish
Pages (from-to)16383-16391
Number of pages9
JournalChemistry - A European Journal
Volume26
Issue number69
DOIs
Publication statusPublished - 2020 Dec 9

Keywords

  • bipolar host materials
  • density functional calculations
  • fluorescence
  • high external quantum efficiency
  • organic light-emitting diodes
  • thermally activated delayed fluorescence

ASJC Scopus subject areas

  • Catalysis
  • Organic Chemistry

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