Jeong Keun Park

Efficient deep-blue and white organic light-emitting diodes based on triphenylsilane-substituted anthracene derivatives

A series of anthracene derivatives with a triphenylsilane end-capping group, (9,9-dimethyl-2-(10-phenylanthracen-9-yl)-9H-fluoren-7-yl)triphenylsilane (PAFTPS), 9,10-bis(9,9-dimethyl-2-(triphenylsilyl)-9H-fluoren-7-yl)anthracene (BFPSA), (9,9-dimethyl-2-(9,10-diphenylanthracen-2-yl)-9H-fluoren-7-yl)triphenylsilane (DPA-2FTPS), and (9,10-eiphenylanthracen-2-yl)triphenylsilane (DPA-2TPS), have been designed, synthesized, and characterized. A device incorporating PAFTPS as the emissive layer exhibited a high external quantum efficiency of 2.02% at 20 mA cm−2 with color coordinates of (0.152, 0.072) as a non-doped blue emitter. At even higher efficiency, an external quantum efficiency up to 2.32% at 20 mA cm−2 with color coordinates of (0.155, 0.076) was obtained when doped with the blue fluorescent material, 3-(N-phenylcarbazol)vinyl-p-terphenyl (PCVtPh). Furthermore, an efficient white OLED with an external quantum efficiency, a luminous efficiency and color coordinates of 4.18%, 9.14 cd A−1 at 1000 cd m−2 and (0.43, 0.41) at 1000 cd m−2 was demonstrated by exploiting this highly efficient blue fluorescent material (PAFTPS) as a host in the blue emitting layer.

Highly Efficient Blue Light-Emitting Diodes Using New Fluorescent Host Materials Based on Naphthalenes

The naphthalene-based blue materials 4,4′-(Dinaphthalen-2-yl)-1,1′-binaphthyl (DNBN) and 1,4-(Dinaphthalen-2-yl)-naphthalene (DNN) were designed and synthesized for OLEDs. A device (non-doped) employing DNN as the emitter exhibited a maximum luminance, luminous efficiency, and external quantum efficiency of 1120 cd/m2, 1.40 cd/A, and 3.83%, respectively. Moreover, its CIE coordinates (0.152, 0.069) are very close to the NTSC blue standard of (0.14, 0.08). In order to improve EL efficiencies, these materials were used as the blue host materials for the blue dopants PFVtPh and PCVtPh. A device 1b (PFVtPh-doped) showed high EL efficiencies of 5.24 cd/A, 2.75 lm/W, and 3.82% at 20 mA/cm2.

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.

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.