posted on 2021-10-11, 07:29authored byDong Won Lee, Jinhyo Hwang, Hyung Jong Kim, Hyoseong Lee, Jung Min Ha, Han Young Woo, Sungnam Park, Min Ju Cho, Dong Hoon Choi
Three
V-shaped host molecules with a cyclohexane linker were successfully
synthesized for thermally activated delayed fluorescence organic light-emitting
diodes (TADF-OLEDs). The unipolar host molecules, BBCzC and BTDC,
contained two 9-phenyl-9H-3,9′-bicarbazole
(PBCz) moieties and two 2,12-di-tert-butyl-7-phenyl-5,9-dioxa-13b-boranaphtho[3,2,1-de]anthracene (PDBNA)
moieties, respectively. BCzTC, a bipolar host molecule, consisted
of a donor unit, PBCz, and an acceptor unit, PDBNA, connected by a
cyclohexane linker. Three host molecules showed good solubility in
various organic solvents, making them suitable for solution processing.
Among the solution-processed green TADF-OLEDs using three host molecules
and a green TADF emitter, the one with BCzTC showed the highest external
quantum efficiency of up to 30% with a high power efficiency of 71
lm W–1 and a current efficiency of 102 cd A–1. Compared with BBCzC and BTDC, BCzTC exhibited a
relatively high photoluminescence quantum yield (PLQY), an excellent
balance in hole and electron transport properties in the emitting
layer, and more efficient energy transfer to the emitter, giving such
an excellent device performance.