107782-99-0Relevant academic research and scientific papers
A ternary phosphine oxide host featuring thermally activated delayed fluorescence for blue PHOLEDs with >20% EQE and extremely low roll-offs
Li, Chenyu,Fan, Xuefeng,Han, Chunmiao,Xu, Hui
, p. 6747 - 6754 (2018)
Development of high-performance blue organic light-emitting diodes (OLEDs) is one of the main challenges because efficient host-dopant energy transfer is necessary to develop highly efficient OLEDs. In this study, an effective molecular design strategy for blue phosphorescent hosts with high triplet (T1) energy and the feature of thermally activated delayed fluorescence (TADF) has been demonstrated using a ternary donor-acceptor-acceptor (D-A-A) molecule, DCDPOTZ, in which carbazole, triazine and diphenylphosphine oxide are incorporated as donor and acceptors. DCDPOTZ achieves the typical characteristics of TADF with a high T1 energy level of 2.93 eV and a small singlet-triplet splitting of 0.27 eV, accompanied by the ambipolar property. Its host characteristics are further improved by its diphenylphosphine oxide group with large steric hindrance for suppressing intermolecular interaction-induced quenching. By adopting bis(4,6-difluorophenylpyridinato)tetrakis((1-pyrazolyl)borate)iridium(iii) (FIr6) as a dopant, DCDPOTZ successfully realizes 100% host-dopant energy transfer efficiency. As a consequence, DCDPOTZ endowed its FIr6-based devices with extremely low driving voltages, the state-of-the-art external quantum efficiency (EQE) of up to 22.7%, and 100% internal quantum efficiency. At 1000 nits, the EQE is still beyond 20%, corresponding to a roll-off as low as 11%, which is one of the lowest values reported to date for blue phosphorescent OLEDs.
High-efficiency hyperfluorescent white light-emitting diodes based on high-concentration-doped TADF sensitizer matricesviaspatial and energy gap effects
Duan, Chunbo,Han, Chunmiao,Wang, Zicheng,Xin, Ying,Xu, Hui,Zhang, Jing
, p. 159 - 169 (2021/12/31)
Despite the success of monochromatic hyperfluorescent (HF) organic light-emitting diodes (OLEDs), high-efficiency HF white OLEDs (WOLEDs) are still a big challenge. Herein, we demonstrate HF WOLEDs with state-of-the-art efficiencies, featuring a quasi-bilayer emissive layer (EML) composed of an ultrathin (0.1 nm) blue fluorescence (FL) emitter (TBPe) layer and a layer of thermally activated delayed fluorescence (TADF) sensitizer matrix heavily doped with a yellow FL emitter (TBRb, 3%). Based on an asymmetric high-energy-gap TADF sensitizer host (PhCzSPOTz), such an “ultrathin blue emitting layer (UTBL)” strategy endowed the HF WOLEDs with a record power efficiency of ～80 lm W?1, approaching the level of fluorescent tubes. Transient photoluminescence (PL) and electroluminescence (EL) kinetics demonstrate that the spatial separation of TBPe from the TADF sensitizer and TBRb, and the large energy gap between the latter two effectively suppress triplet leakage, in addition to suppressing triplet diffusion in the PhCzSPOTz matrix with anisotropic intermolecular interactions. These results provide a new insight into the exciton allocation process in HF white light-emitting systems.
