Efficient near-infrared emission based on donor-acceptor molecular architecture: The role of ancillary acceptor of cyanophenyl

Herein, a new near-infrared (NIR) material, 4-(9-(4-(diphenylamino)phenyl)naphtho[2,3-c][1,2,5]thiadiazol-4-yl)benzonitrile (TPA-NZC), was designed and synthesized with the incorporation of an ancillary acceptor (cyanophenyl) into the donor-acceptor (D-A) molecular backbone of a red emitter TPA-NZP (4,9-diphenylnaphtho[2,3-c][1,2,5]thiadiazole). Compared with TPA-NZP, TPA-NZC exhibits an NIR emission (λmax = 710 nm) with a large redshift, as well as a maintained photoluminescence efficiency (ηPL) of 17% in film. Moreover, the non-doped OLED based on TPA-NZC emitter exhibits an excellent NIR emission at 702 nm with a maximum EQE of 1.2%, while the doped device achieves a deep-red emission at 656 nm with a maximum EQE of 3.2%. This work further verifies the reliability of “hot exciton” and hybridized local and charge-transfer state (HLCT) mechanism, as well as provides a strategy to design a narrow bandgap light-emitting material by introducing cyanophenyl as an ancillary acceptor in D-A systems.