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Blue TADF Emitters Based on B-Heterotriangulene Acceptors for Highly Efficient OLEDs with Reduced Efficiency Roll-Off

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Abstract
The design of robust boron acceptors plays a key role in the development of boron-based thermally activated delayed fluorescence (TADF) emitters for the realization of efficient and stable blue organic light-emitting diodes (OLEDs). Herein, we report a set of donor (D)-acceptor (A)-type blue TADF compounds (1-3) comprising triply bridged triarylboryl acceptors, the so-called B-heterotriangulenes, which differ depending on the identity of one of the bridging groups: methylene (1), dimethylmethylene (2), or oxo (3). The X-ray crystal structures of 2 and 3 reveal a highly twisted D-A connectivity and a completely planar geometry for the B-heterotriangulene rings. All compounds exhibit blue emissions with the unitary photoluminescence quantum yields and small singlet-triplet energy splitting (<0.1 eV) in their doped host films. The compounds exhibit a fast reverse intersystem crossing rate (k(RISC) approximate to 10(6) s(-1)) with short-lived delayed fluorescence (tau(d) approximate to 2 mu s), which is found to be promoted by the strong spin-orbit coupling between the local triplet excited state ((LE)-L-3, T-2) and singlet (S-1) states. Using compounds 1-3 as the emitters, highly efficient blue TADF-OLEDs are realized. The devices based on the emitters with B-heterotriangulenes exhibit better performances than the device incorporating a singly bridged reference emitter over the whole luminance range. Notably, the device based on the fully dimethylmethylene-bridged emitter (2) achieves the highest maximum external quantum efficiency (EQE) of 28.2% and the lowest efficiency roll-off, maintaining a high EQE value of 21.2% at 1000 cd/m(2).
Author(s)
이영훈이우찬이태환이동균정재훈유승협이민형
Issued Date
2021
Type
Article
Keyword
thermally activated delayed fluorescencedonor?acceptorB-heterotrianguleneblue emitterOLEDs
DOI
10.1021/acsami.1c10653
URI
https://oak.ulsan.ac.kr/handle/2021.oak/9653
https://ulsan-primo.hosted.exlibrisgroup.com/primo-explore/fulldisplay?docid=TN_cdi_proquest_miscellaneous_2572526387&amp;context=PC&amp;vid=ULSAN&amp;lang=ko_KR&amp;search_scope=default_scope&amp;adaptor=primo_central_multiple_fe&amp;tab=default_tab&amp;query=any,contains,Blue%20TADF%20Emitters%20Based%20on%20B-Heterotriangulene%20Acceptors%20for%20Highly%20Efficient%20OLEDs%20with%20Reduced%20Efficiency%20Roll-Off&amp;offset=0&amp;pcAvailability=true
Publisher
ACS APPLIED MATERIALS INTERFACES
Location
미국
Language
영어
ISSN
1944-8244
Citation Volume
13
Citation Number
38
Citation Start Page
45778
Citation End Page
45788
Appears in Collections:
Natural Science > Chemistry
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