Efficient Near-Infrared Emission by Adjusting the Guest-Host Interactions in Thermally Activated Delayed Fluorescence Organic Light-Emitting Diodes

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 are used to match the thermally activated delayed fluorescence 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 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.