Bo Min Seo

Diphenylaminoarene/Chromene-containing Red Fluorescent Emitters for Organic Light-Emitting Diodes

In this study, we synthesized new 2-(2-(4-(diphenylamino)styryl)-4H-chromen-4-ylidene) malononitrile (DCCPA) derivatives with different π-conjugation aromatic spacer groups between the diphenylamine and (chromen-4-ylidene)malononitrile moieties of the DCCPA. To explore the electroluminescence properties of these materials, multilayered OLEDs were fabricated with a device stricture of: Indium Tin Oxide (ITO) (170 nm)/N,N’-diphenyl-N,N’-(1-napthyl)-(1,1’-phenyl)-4,4’-diamine (NPB) (50 nm)/2-methyl-9,10-bis-2-naphthyl anthracene (MADN):Red dopants 1 (5, 10%) (30 nm)/bis-(2-methyl-8-quinolinolato-N1,O8)-(1,1’-biphenyl-4-olato)aluminum (Balq) (30 nm)/Liq (2 nm)/Al (10 nm). A device using Red 1 showed a maximum luminance of 1030 cd/m2 at 10.0 V, with maximum luminous, power, and quantum efficiencies of 0.94 cd/A, 0.54 lm/W, and 1.11%, respectively. The CIE coordinates of this device were (0.61, 0.35) at 7.0 V, a stable color chromaticity at various voltages.

Efficient White Organic Light-Emitting Diodes with Dual Blue Emitting Layer

We have demonstrated efficient phosphorescent white organic light-emitting diodes (PHWOLEDs) by using iridium (III) bis(1-phenyl(quinolinato-N,C2′))acetylacetonate doped in 4,4,4-tris(N-carbazolyl)-triphenylamine as phosphorescent red emitting layer and iridium (III) bis[(4,6-di-fluoropheny)-pyridinato-N,C2] picolinate doped in dual blue-emitting layer (D-BEML), N,N′-dicarbazolyl-3,5-benzene and 2,2′,2″″-(1,3,5-benzenetryl) tris(1-phenyl)- 1H-benzimidazol, respectively. D-BEML structure have broad exciton formation zone than single BEML. The optimized PHWOLEDs showed an external quantum efficiency of 5.93%, current efficiency of 11.54 cd/A, and Commission Internationale de L’Eclairage coordinates of (0.45, 0.37) at 1000 cd/m2.

Efficient Red Organic Light-Emitting Diodes Using 2-(2-(4-Pentylbicyclo[2.2.2]octan-1-yl)-6-(2-(1,1,7-trimethyl-7-triphenysiliyllethyl-1,2,3,5,6,7-hexahydropyrido[3,2,1-ij]quinolin-9-yl)vinyl)-4H-pyran-4-ylidene)malononitrile as a Fluorescent Red Emitter

The authors have demonstrated red organic light-emitting diodes (OLEDs) using a new fluorescent red emitter, 2-(2-(4-pentylbicyclo[2.2.2]octan-1-yl)-6-(2-(1,1,7-trimethyl-7-triphenysiliyllethyl-1,2,3,5,6,7-hexahydropyrido[3,2,1-ij]quinolin-9-yl)vinyl)-4H-pyran-4-ylidene)malononitrile (DCJTPSO), achieved the maximum external quantum efficiency (EQE) of 2.06%, current efficiency (CE) of 3.83 cd/A, and Commision Internationale De L’Eclairage (CIEx,y) coordinates of (0.58, 0.40) at 0.029 mA/cm2 in comparison with control device using 4-(dicyanomethylene)-2-tert-butyl- 6-(1,1,7, 7-tetramethyljulolidin-4-yl-vinyl)- 4H-pyran which showed the maximum EQE of 1.07%, CE of 1.41 cd/A and CIEx,y coordinates of (0.61, 0.38) at 0.11 mA/cm2. This result showed that the high performance of red device using DCJTPSO showed easier electron trapping directly on the emitter molecule.

Hybrid White Organic Light-Emitting Diodes with Reduced Efficiency Roll-Off

The authors have demonstrated hybrid white organic light-emitting diodes (HWOLEDs) with reduced efficiency roll-off. It was shown that HWOLEDs fabricated with {9,9-dimethyl-7-[10-(naphthalen-2-yl)anthracen-9-yl]-9H-fluoren-2-yl} triphenylsilane (ANFTPS) as the blue host have the maximum external quantum efficiency of 9.92%, power efficiency of 14.51 lm/W, and reduced efficiency roll-off 2.0 times that of the control white device. The deep highest occupied molecular orbital of ANFTPS of the optimized white device adequately brocks holes and confines excitons in emitting layers. The white device also exhibited a more stable color shift from low to high current density than did the control white device.