Kum Hee Lee

Highly efficient white organic light-emitting diodes using two emitting materials for three primary colors (red, green, and blue)

The authors have demonstrated highly efficient white organic light-emitting diodes (WOLEDs) by using two emissive materials as a dopant, 1,4-bis[2-(7-N-diphenyamino-2-(9,9-diethyl-9H-fluoren-2-yl)) vinyl] benzene (DAF-ph) and iridium(III) bis(5-acetyl-2-phenylpyridinato-N,C2′) acetylacetonate ((acppy)2Ir(acac)). It was found that the OLED fabricated in this study emitted a white color consisting of three primary colors (red, green, and blue). The luminance-voltage (L-V) characteristics of the WOLEDs showed the maximum luminance of 30500cd∕m2 at 14V and the maximum luminous efficiency of 38.0cd∕A, respectively. The CIEx,y coordinates of the WOLED also showed (x=0.33, y=0.40) at 10V.

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.

Hybrid spacer for high-efficiency white organic light-emitting diodes

High-efficient white organic light-emitting diodes (WOLEDs) were fabricated by using the following three different emitting materials: 4″-(2,2-diphenylvinyl)-1-[4-(N,N-diphenylamino)-styryl]-terphenyl for blue emission, fac-tris(2-phenypyridine) iridium(III) for green emission, and bis(5-benzoyl-2-phenylpyridinato-C,N)iridium(III) (acetylacetonate) for red emission. For higher efficiency, a hybrid spacer (HS) was inserted between each emissive layer (blue-red, red-green, and green-blue emissive layers). It was found that the WOLEDs using HS showed maximum power efficiency of 28.69lm∕W, maximum external quantum efficiency of 13.1%, and Commission Internationale de I’Eclairage coordinates (CIEx,y) of (x=0.37,y=0.37).

tert-Butylated spirofluorene derivatives with arylamine groups for highly efficient blue organic light emitting diodes

A series of tert-butylated spirofluorene derivatives incorporating a diphenylaminoaryl-vinyl group was synthesized via the Horner–Wadsworth–Emmons olefination and a Suzuki cross-coupling reaction. To examine the electroluminescent properties of these materials, multilayered OLEDs were fabricated into the following device structure: ITO/DNTPD/NPB/MADN:blue dopant materials 1–14/Alq3/Liq/Al. All devices showed efficient blue emission. In particular, one device exhibited highly efficient sky blue emission with a maximum luminance of 25 100 cd m−2 at 8.5 V, as well as luminous, power and external quantum efficiencies of 9.5 cd A−1, 5.1 lm W−1 and 6.7% at 20 mA cm−2, respectively. The peak wavelength of electroluminescence was 458 and 484 nm with CIEx,y coordinates of (0.14, 0.21) at 8.0 V. In addition, a deep blue device with CIEx,y coordinates of (0.15, 0.15) at 8.0 V showed a luminous efficiency and external quantum efficiency of 3.8 cd A−1 and 3.3% at 20 mA cm−2, respectively.

Enhanced life time and suppressed efficiency roll-off in phosphorescent organic light-emitting diodes with multiple quantum well structures

We demonstrate red phosphorescent organic light-emitting diodes (OLEDs) with multiple quantum well structures which confine triplet exciton inside an emitting layer (EML) region. Five types of OLEDs, from a single to five quantum wells, are fabricated with charge control layers to produce high efficiencies, and the performance of the devices is investigated. The improved quantum efficiency and lifetime of the OLED with four quantum wells, and its suppressed quantum efficiency roll-off of 17.6%, can be described by the increased electron–hole charge balance owing to the bipolar property as well as the efficient triplet exciton confinement within each EML, and by prevention of serious triplet–triplet and/or triplet–polaron annihilation as well as the Forster self-quenching due to charge control layers.

Synthesis of Ir(III) Complexes Containing Meta-Carbonylated Phenylpyridine Ligand for Phosphorescent Organic Light-Emitting Diodes

The photophysical characteristics of phosphorescent Ir(III) complexes 1–3 were investigated to determine their suitability as candidates for green light-emitting materials for OLEDs. To evaluate the EL properties of using these compounds as dopant in the emitting layer, multilayered devices were designed as green-light-emitting device having the following configuration: ITO/NPB (30 nm)/Ir(III) complexe 1 (5 and 10 wt.%) doped in CBP (30 nm)/BCP (10 nm)/Alq3 (40 nm)/Liq/Al were fabricated. An OLED device employing 1 as a dopant exhibits the performance with a maximum luminance of 46000 cd/m2 at 14.0 V. The luminous efficiency, power efficiency were 17.3 cd/A, 6.97 lm/W at 20 mA/cm2, respectively. Also, this device shows green emission with CIE coordinates of (0.247, 0.594) at 10.0 V.

Synthesis and Electroluminescent Properties of Blue Fluorescent Triphenylamine Substituted Anthracene Derivatives for OLEDs

We describe the electroluminescent properties of blue fluorescent materials based on mono(triphenylamino)anthracene derivatives synthesized via Suzuki cross coupling reactions. To explore the electroluminescent properties of materials 1–3, multilayered OLEDs were fabricated and all devices exhibited efficient blue emissions. Among those, device 1, with CIE x,y coordinates of (0.159, 0.166) at 12.0 V, exhibited the best performance, with a maximum luminance of 7306 cd/m2 at 12.0 V, and luminous and power efficiencies of 4.95 cd/A and 1.83 lm/W at 20 mA/cm2, respectively.

Blue Organic Light-Emitting Diodes Containing Anthracene Derivatives With End-Capping Phenyl Group

We have synthesized and characterized new blue host materials for OLEDs; 9,10-di-o-tolylanthracene (1), 2-tert-butyl-9,10-diphenylanthracene (2), 10,10′-diphenyl-9,9′-bianthracene (3), and 1,4-bis(10-phenylanthracen-9-yl)benzene (4). To explore electroluminescent properties of these materials, multilayered OLEDs with the configuration of ITO/NPB (50 nm)/Blue emitters (1–4) (30 nm)/Liq (2 nm)/Al (100 nm) were fabricated. Among those non-doped devices, the device 4a employing 4 as an emitter showed high efficiencies of 4.11 cd/A, 3.31 lm/W, and 2.35%, respectively. The device 2b employing 2 as host material for PFVtPh blue dopant material exhibited excellent efficiencies with 5.64 cd/A, 4.14 lm/W, and 4.54%.

P-164: Highly Efficient White Organic Light-Emitting Diodes Using Two Emitting Materials for Three Primary Colors (Red, Green and Blue)

These results have demonstrated the highly efficient white organic light-emitting diodes (WOLEDs) with two separated emissive materials for the three primary colors, red, green, and blue, using blue fluorescent and red phosphorescent dopants. The two devices with the optimum structure showed a maximum luminance of 30500 and 20400 cd/m2 and a luminous efficiency of 38.0 and 32.7 cd/A. Furthermore, device B showed better CIEx,y coordinates of (x=0.36, y=0.35) at 10V. We expect that the WOLEDs fabricated using device structures and materials described here may be applicable for backlights in liquid crystal displays.

Non-Doped Blue OLEDs Based on 9,9′-Dimethylfluorene Containing 10-Naphthylanthracene Derivatives

A series of blue fluorescent materials 1–3 based on 10-(2-napthyl)-anthracene derivatives with the diverse aromatic groups were synthesized and multilayer non-doped devices using them as emitting materials were fabricated. All OLED devices using these materials emit deep blue light of 446–456 nm. In particular, device 3 exhibited highly efficient blue emissions with the luminous efficiency of 3.89 cd/A, a power efficiency of 2.47 lm/W, Quantum Efficiency of 3.03% at 20 mA/cm2, and CIEx,y coordinates of (0.163, 0.149) at 6 V. Also, device 2 showed the efficient deep-blue emission with CIE coordinates of (x = 0.151, y = 0.104) at 6 V.