High-performance bipolar host materials for blue TADF devices with excellent external quantum efficiencies

Ju Sik Kang, Tae Ryang Hong, Hyung Jong Kim, Young Hoon Son, Raju Lampande, Byoung Yeop Kang, Chiho Lee, Jong Kwan Bin, Bang Sook Lee, Joong Hwan Yang, Jinwuk Kim, Sungnam Park, Min Ju Cho, Jang Hyuk Kwon, Dong Hoon Choi

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47 Citations (Scopus)

Abstract

New bipolar host molecules composed of carbazole, pyridoindole, and dibenzothiophene (DBT) were synthesized for blue thermally activated delayed fluorescence (TADF)-based organic light-emitting diodes (OLEDs). 2,8-Di(9H-carbazol-9-yl)dibenzo[b,d]thiophene, 9-(8-(9H-carbazol-9-yl)dibenzo[b,d]thiophen-2-yl)-9H-pyrido[2,3-b]indole, and 2,8-bis(9H-pyrido[2,3-b]indol-9-yl)dibenzo[b,d]thiophene were prepared based on the selective reactivity at the 2,8-positions of DBT. The new symmetric and asymmetric host materials exhibited high triplet energies (2.89-2.95 eV). 4,5-Di(9H-carbazol-9-yl)phthalonitrile (2CzPN) was selected as an emitting dopant for achieving sky-blue emissions in TADF-OLEDs. 2CzPN-doped TADF-OLEDs, whose configuration is ITO (50 nm)/HATCN (7 nm)/TAPC (75 nm)/host:6% 2CzPN (20 nm)/TmPyPB (50 nm)/LiF (15 nm)/Al (100 nm), showed low driving voltages and high external quantum efficiencies (EQEs). These results are attributed to the well-controlled bipolar character of the host giving a better charge balance in the emitting layer. In particular, the device containing ZDN:6% 2CzPN showed an unprecedentedly high EQE of 25.7% (at 0.074 mA cm-2).

Original languageEnglish
Pages (from-to)4512-4520
Number of pages9
JournalJournal of Materials Chemistry C
Volume4
Issue number20
DOIs
Publication statusPublished - 2016
Externally publishedYes

ASJC Scopus subject areas

  • Chemistry(all)
  • Materials Chemistry

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    Kang, J. S., Hong, T. R., Kim, H. J., Son, Y. H., Lampande, R., Kang, B. Y., Lee, C., Bin, J. K., Lee, B. S., Yang, J. H., Kim, J., Park, S., Cho, M. J., Kwon, J. H., & Choi, D. H. (2016). High-performance bipolar host materials for blue TADF devices with excellent external quantum efficiencies. Journal of Materials Chemistry C, 4(20), 4512-4520. https://doi.org/10.1039/c6tc00385k