9,10-Bis(3′,5′-diphenylphenyl)anthracene [MAM], 9-(3′,5′-diphenylphenyl)-10-(3‴,5‴-diphenylbiphenyl-4″-yl)anthracene [MAT], and 9,10-bis(3″,5″-diphenylbiphenyl-4′-yl)anthracene [TAT] were newly synthesized through boration and Suzuki aryl–aryl coupling reactions. We have demonstrated that the EL performance of blue-light emitters can be optimized and improved by varying the chemical structures of the side groups. In the thin film state, the three materials exhibit PL_max values in the range of 439–445 nm. MAM, MAT, and TAT all have high T_g values above 120 °C; TAT has the highest T_g value, above 150 °C. This is twice as high as that of DPVBi (64 °C) and is much higher than that of MADN (120 °C) as well. It also exhibits excellent color coordinates (0.156, 0.088), which are very close to the NTSC blue standard, and an external quantum efficiency of 7.18%, twice that of MADN, which are the best reported results for deep-blue OLED emitters.

New blue fluorescent compounds containing tetra-substituted ethylene moieties have been designed and synthesized. These materials, 1,2-di(4′-tert-butylphenyl)-1,2-bis(4′-(anthracene-9-yl)phenyl)ethene [BPBAPE, 1A], 1,2-diphenyl-1,2-bis(4′-(anthracene-9-yl)phenyl)ethene [PBAPE, 1B], 9,10-bis(4-(1,2,2-tris(4-tert-butylphenyl)vinyl)phenyl)anthracene [BTBPPA, 2A], and 9,10-bis(4-(1,2,2-triphenylvinyl)phenyl)anthracene [BTPPA, 2B], were synthesized through Suzuki and McMurry reactions. By fabricating multilayered non-doped OLED devices using these new blue materials, we achieved luminance efficiencies of 4.00 lm W⁻¹ (10.33 cd A⁻¹ at 8.1 V) for BPBAPE [1A] and 1.82 lm W⁻¹ (3.93 cd A⁻¹ at 6.8 V) for BTPPA [2B] at 10 mA cm⁻². The maxima in the electroluminescence spectra of ITO/2-TNATA (60 nm)/NPB (15 nm)/BPBAPE [1A] and BTPPA [2B] (30 nm)/Alq₃ (30 nm)/LiF (1 nm)/Al (200 nm) devices were found to be 475 and 452 nm respectively. The BPBAPE [1A] and BTPPA [2B] devices exhibited sky blue emission (0.195, 0.303) and deep blue emission (0.159, 0.135) at 10 mA cm⁻² respectively.

We describe two novel blue emission materials based on a new type of dual core concept. 1-Phenyl-6-(10-phenyl-anthracen-9-yl)-pyrene (Ph-AP-Ph) and 1-[1,1′;3′,1′′]terphenyl-5′-yl-6-(10-[1,1′;3′,1′′]terphenyl-5′-yl-anthracen-9-yl)-pyrene (TP-AP-TP) were synthesized through boronylation and Suzuki coupling reactions. The T_g values of Ph-AP-Ph and TP-AP-TP were 228 °C and 243 °C, respectively, compared to values of 135 °C and 139 °C for the single core materials 9-(3′,5′-diphenylphenyl)-10-(3′′′,5′′′-diphenylbiphenyl-4′′-yl)anthracene (MAM) and 1,6-bis-[1,1′;3′,1′′]terphenyl-5′-yl-pyrene (TP-P-TP). One of the dual core derivatives, TP-AP-TP, exhibited an EL_max value of 456 nm and a high luminance EQE of 7.51% when used in an EL device. The dual core chromophore materials had narrower PL and EL spectra and better thermal properties than the single core chromophore materials. A device based on TP-AP-TP showed twice the lifetime of a device based on the commercialized material, 2-methyl-9,10-bis(naphthalen-2-yl)anthracene (MADN).

To explain the origin of extremely high efficiencies of deep-blue fluorescent organic light-emitting diodes (OLEDs) with anisotropic-shaped anthracene derivatives, the enhancements of singlet-exciton generation efficiency and outcoupling efficiency were investigated by transient electroluminescence measurement and variable angle spectroscopic ellipsometry, respectively. Both the delayed fluorescence from singlet excitons generated via triplet-triplet annihilation and the outcoupling enhancement by dipole orientation of emitters were found to contribute to the high external quantum efficiencies of the devices. This dual efficiency enhancement is important for understanding and further improving high-performance fluorescent OLEDs.