posted on 2021-12-16, 15:33authored byJinhyo Hwang, Chang Woo Koh, Jung Min Ha, Han Young Woo, Sungnam Park, Min Ju Cho, Dong Hoon Choi
In
this study, we demonstrated two deep-blue TADF emitters, BO-tCzPhICz
and BO-tCzDICz, for solution-processable thermally activated delayed
fluorescence organic light-emitting diodes (TADF-OLEDs). They were
synthesized by employing an organoboron acceptor and 9-(3,6-di-tert-butyl-9H-carbazol-9-yl)-5-phenyl-5,12-dihydroindolo[3,2-a]carbazole (tCzPhICz) and 12-(3,6-di-tert-butyl-9H-carbazol-9-yl)-15H-diindolo[2,3-b:1′,2′,3′-lm]carbazole
(tCzDICz) as bulky aryl-annulated [3,2-a] carbazole
donors, respectively. Both emitters showed sufficient solubility in
organic solvents, narrow deep-blue emission, and small energy difference
(ΔEST) between singlet and triplet
states, which can be applied to solution-processable deep-blue TADF-OLEDs.
Solution-processed OLEDs exploiting these TADF emitters displayed
deep-blue electroluminescence with CIEy <0.1,
and high external quantum efficiencies of 17.8 and 14.8% were observed
for BO-tCzPhICz and BO-tCzDICz, respectively. The emitter bearing
bulky ICz-based donating units shows highly promising potential for
high-efficiency solution-processable deep-blue TADF-OLEDs.