Two new different types of fused-ring heterocycles based on the carbazole and naphthalene, that is, 10-bromine-7-hexyl-7monoaza[6]helicene (7) and 14-hexyl-11-(thiophen-2-yl)-14Hphenanthro[4, 3-b]carbazole (10) were successfully synthesized through the introduction of bromine and thiophene subtituents into 9-Hexyl-9-carbazole-3-carbaldehyde. Their structures were fully characterized by 1 H NMR, 13 C NMR, mass spectroscopy and single-crystal X-ray diffraction pattern. Single-crystal structures revealed that compound 10 possessed less distortion and deformation, and better planarity than compound 7. Compounds 7 and 10 had good solubility and thermal stability (T d = 236.82 8C for 7, T d = 214.96 8C for 10). These compounds had absorption maximum peaks at 319 nm for 7, 337 nm for 10, and emitted blue light with the peaks at 435 nm for 7, 447 nm for 10 in dichloromethane. The fluorescence quantum yields of compounds 7, 10 in different solvents were measured in the range of 8% -18%, 35% -74%, respectively. These results showed that introducing the functional substituent group of thiophene to the carbazole could not only transform photocyclization products from helicenes into other types of fusedring heterocyclic compounds but also increase the fluorescence quantum yields of compound 10 by more than three and half times. The simple synthetic method would pave the way for obtaining fused-ring heterocycles with diverse types and various properties.[a] X.
Due to the strong concentration quenching effect, the development of non-doped devices with excellent performance is limited. Herein, a novel thermally activated delayed fluorescence (TADF) emitter which contain Spiro[anthracene-9(10H),9'-[9H]fluoren]-10-one (9-FAO) and 9,9-dimethyl-9,10-dihydroacridine (DMAC) was designed and synthesized. The non-doped OLED device by using 2-(9, 9-dimethylacridin-10(9H)-yl)-10H-spiro[anthracene-9,9'- fluoren]-10-one (DMTO-DMAC) as emitter achieved a superior current efficiency (CE) of 35.2 cd/A and maximum external quantum efficiency (EQE) of 11.3% with emission peak at 516nm. This work demonstrates the feasibility of increasing intermolecular distance to obtain highly efficience non-doped devices.
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