Asymmetric Host Molecule Bearing Pyridine Core for Highly Efficient Blue Thermally Activated Delayed Fluorescence OLEDs
- Authors
- Yoon, Jiwon; Kim, Seong Keun; Kim, Hyung Jong; Choi, Suna; Jung, Sang Won; Lee, Hyuna; Kim, Jun Yun; Yoon, Dae-Wi; Han, Chang Wook; Chae, Weon-Sik; Kwon, Jang Hyuk; Cho, Min Ju; Choi, Dong Hoon
- Issue Date
- 9-12월-2020
- Publisher
- WILEY-V C H VERLAG GMBH
- Keywords
- bipolar host materials; density functional calculations; fluorescence; high external quantum efficiency; organic light-emitting diodes; thermally activated delayed fluorescence
- Citation
- CHEMISTRY-A EUROPEAN JOURNAL, v.26, no.69, pp.16383 - 16391
- Indexed
- SCIE
SCOPUS
- Journal Title
- CHEMISTRY-A EUROPEAN JOURNAL
- Volume
- 26
- Number
- 69
- Start Page
- 16383
- End Page
- 16391
- URI
- https://scholar.korea.ac.kr/handle/2021.sw.korea/50823
- DOI
- 10.1002/chem.202002655
- ISSN
- 0947-6539
- 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 (T-1=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.
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