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Two solution-processible new triplet bipolar host molecules, 4,4′-bis[N-(1-naphthyl)-N(3-pyridinylamino]biphenyl (NPyB) and 4,4′-bis [N-(3-quinolinyl)-N-phenylamino]biphenyl (QuPB) were synthesized and characterized for phosphorescent organic light-emitting diodes (PHOLEDs). They exhibit good triplet energies as 2.3–2.4 eV for red PHOLEDs and show good amorphous film characteristics with high solubility, allowing a solution processing. The NPyB and QuPB hosts were evaluated for soluble red PHOLEDs with ITO/PEDOT:PSS/Ir complex:host/TPBI/LiF/Al structure. A maximum light output of 14,440 cd/m2, driving voltage of 5.9 V, external quantum efficiency of 14.2%, and maximum current/power efficiencies of 21.0 cd/A and 11.3 lm/W have been achieved by NPyB host and bis(2-phenylquinoline(acetylacetonate)iridium (Ir(phq)2acac) red dopant.

The homoleptic Ir(III) complex, fac-tris{2-(3′-trimethylsilylphenyl)-5-trimethylsilylpyridinato}iridium, has been synthesized and characterized to investigate the effect of the substitution of bulky silyl groups on the photophysical properties and electroluminescence (EL) characteristics of Ir(ppy)3 (ppy = 2-phenylpyridine). The absorption, emission, cyclic voltammetry and electroluminescent performance of the complex have also been evaluated. A power efficiency of 17.3 lm/W at 10 mA/cm2 compared to 11.7 lm/W for Ir(ppy)3 is achieved with the new complex as a dopant in phosphorescent organic light-emitting diodes (OLEDs). In addition, the complex shows a narrow emission band of a small full width at half-maximum (fwhm, ca. 50 nm) value.

The new amorphous molecular material, 2,5-bis(4-triphenylsilanyl-phenyl)-[1,3,4]oxadiazole, that functions as good hole blocker as well as electron transporting layer in the phosphorescent devices. The obtained material forms homogeneous and stable amorphous film. The new synthesized showed the reversible cathodic reduction for hole blocking material and the low reduction potential for electron transporting material in organic electroluminescent (EL) devices. The fabricated devices exhibited high performance with high current efficiency and power efficiency of 45 cd/A and 17.7 lm/W in 10 mA/cm2, which is superior to the result of the device using BAlq (current efficiency: 31.5 cd/A and power efficiency: 13.5 lm/W in 10 mA/cm2) as well-known hole blocker. The ITO/DNTPD/α-NPD/6% Ir(ppy)3 doped CBP/2,5-bis(4-triphenylsilanyl-phenyl)-[1,3,4]oxadiazole as both hole blocking and electron transporting layer/Al device showed efficiency of 45 cd/A and maximum brightness of 3000 cd/m2 in 10 mA/cm2.

The new green Ir(III) complex, fac-tris[4-methyl-2-(4′-trimethylsilylph-enyl)pyridine] [Ir(msippy)3], is synthesized and phosphorescent light emitting devices fabricated by using them as triplet emissive dopants. Ir(dsippy)3 in UV-Vis. spectra showed absorption band at 395 nm originating from 1MLCT. The EL devices with configuration of ITO/CuPc (10 nm)/α -NPD (40 nm)/CBP-Ir(msippy)3 (20 nm)/BCP (10 nm)/Alq3 (40 nm)/LiF (1 nm)/Al (100 nm).showed the emission maximum at 516 nm, due to the radiative decay from 3MLCT state to ground state. The 6% doped devices showed the maximum efficiency of 49.9 cd/A and power efficiency 25.3 lm/W. The observed PL quantum efficiency (0.43) of the [Ir(msippy)3] in CH2Cl2 shows slightly higher than that of reported Ir(ppy)3 (Φ = 0.40).

A new 1,3,5-triazine derivative containing the phenothiazine moiety (PTZ-TRZ) has been synthesized for use as a host material of phosphorescent dye. The photoluminescence and electroluminescence pr...