Highly efficient near-infrared thermally activated delayed fluorescence material based on a spirobifluorene decorated donor.

The development of red/near-infrared (NIR) thermally activated delayed fluorescence (TADF) emitters are relatively lagging due to the spin statistics and energy gap law. Herein, we designed and synthesized a new NIR TADF emitter, 3-(4-(9,9′-spirobi[fluorene]-3-yl(phenyl)amino)phenyl)acenaphtho[1,2-b]pyrazine-8,9-dicarboni-trile (SDPA-APDC) , by incorporating a spiro-type electron-donating moiety N , N -diphenyl-9,9′-spirobi[fluorene]-2-amine (SDPA) to an electron-withdrawing unit acenaphtho[1,2- b ]pyrazine-8,9-dicarbonitrile (APDC). The photophysical, electrochemical and thermal properties of SDPA-APDC have been systematically explored. Consequently, the emitter was found high photoluminescence quantum yield (PLQY), narrow bandgap, small singlet-triplet energy gap (Δ E ST) and excellent thermal stability. Furthermore, SDPA-APDC was developed for electroluminescence devices. The doped devices of SDPA-APDC achieved a red emission peak at 696 nm with a maximum external quantum efficiency (EQE) of 10.75%. And the non-doped device exhibited a NIR emission peak at 782 nm with a maximum EQE of 2.55% Image 1 • Designing a near-infrared TADF emitter SDPA-APDC. • The doped and non-doped OLEDs of SDPA-APDC exhibited a maximum external quantum efficiency (EQE) of 10.75% (red emission peak at 696 nm) and 2.55% (NIR emission peak at 782 nm), respectively. • Enriching the design principles of efficient red/NIR TADF emitters based on more different electron donors. [ABSTRACT FROM AUTHOR]