系统间交叉
材料科学
量子效率
有机发光二极管
单重态
荧光
接受者
光致发光
共发射极
激发态
光电子学
光化学
纳米技术
原子物理学
化学
光学
物理
图层(电子)
凝聚态物理
作者
Young Ho Lee,Woochan Lee,Taehwan Lee,Donggyun Lee,Jaehoon Jung,Seunghyup Yoo,Min Hyung Lee
标识
DOI:10.1021/acsami.1c10653
摘要
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 (kRISC ≈ 106 s–1) with short-lived delayed fluorescence (τd ≈ 2 μs), which is found to be promoted by the strong spin–orbit coupling between the local triplet excited state (3LE, T2) and singlet (S1) 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/m2.
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