High Performance NIR OLEDs with Emission Peak Beyond 760 nm and Maximum EQE of 6.39

摘要

Advances in achieving high external quantum efficiency (EQE) of nearinfrared(NIR) organic light-emitting diodes (OLEDs) are lagging behindthat of the visible-light OLEDs, according to the energy gap law. Herein,two structurally simple NIR-phosphorescent Ir(Ⅲ) complexes, DTCNIr andPTCNIr, with the cyclometalated ligands functionalized by the 1-phenylisoquinoline-4-carbonitrile moiety and thieno/benzo[b]thiophene moiety are handilyaccessed within three synthetic steps. The introduction of the cyano unit cansignificantly lower the lowest unoccupied molecular orbitals whereas incorporatingthe conjugated group can elevate the highest occupied molecularorbitals of the newly designed Ir(Ⅲ) complexes. The intramolecular chargetransfer (ICT) transitions are enhanced due to the increased donor–acceptorinteraction inside the metallophosphor. As a result, the emissions are redshiftedto the NIR region with fast radiative decay. A maximum externalquantum efficiency (EQE) of 8.11% with the emission peak at 726 nm forDTCNIr and a maximum EQE of 6.39% with the emission peak at 763 nm forPTCNIr are achieved in the NIR OLEDs by using these Ir(Ⅲ) materials as thedopant emitters, a champion efficiency in the Ir(Ⅲ)-based OLEDs with theemission peak exceeding 760 nm.