Efficient Near-Infrared Emission by Adjusting the Guest-Host Interactions in Thermally Activated Delayed Fluorescence Organic Light-Emitting Diodes
Yun Hu1, Yi Yuan1, Ying-Li Shi1, Dan Li1, Zuo-Quan Jiang*,1 and Liang-Sheng Liao*,1,2
1Jiangsu Key Laboratory for Carbon-Based Functional Materials & Devices, Institute of Functional Nano & Soft Materials (FUNSOM), Soochow University, Suzhou, Jiangsu 215123, China
2Institute of Organic Optoelectronics, Jiangsu Industrial Technology Research Institute (JITRI), Wujiang, Suzhou, Jiangsu 215211, China
Thermally activated delayed ﬂuorescence materials can effectively achieve high efficiency by harvesting singlet and triplet excitons in organic light-emitting diodes (OLEDs). However, the choice of host material has a huge impact on the efficiency of the device, especially for the near-infrared (NIR) luminescent material. In this contribution, a series of host materials were used to match the TADF emitter, 3,4-bis(4-(diphenylamino)phenyl)acenaphtho[1,2-b]pyrazine-8,9-dicarbonitrile (APDC-DTPA), for fabricating NIR OLEDs. All the host materials have the higher triplet energy than that of APDC-DTPA. As the organometallic compound of Zn(BTZ)2 has relatively stronger dipole moment, the electroluminescence spectral peak of doped device shows strong bathochromic shift exceeding 700 nm and changes with doping concentration. Finally, the extremely high external quantum efficiency of 7.8% (with 10 wt% of doping concentration) and 5.1% (with 20 wt% of doping concentration) are achieved with the emission peaks of 710 nm and 728 nm, respectively, which are superior to that of the device based on the other host materials. The approach is feasible to achieve bathochromic shift and highly efficient fluorescent OLEDs.