Seul Ong Kim

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.

Blue-Light-Emitting Bis(diarylamino)stilbene Derivatives: Synthesis, Photophysical Properties, and Highly Efficient OLEDs

New electroluminescent materials, 4,4′-bis(2-naphthyl-4-tert-butylphenylamino)stilbene (1), 4,4′-bis(4-tert-butylphenyl-3,5-di-tert-butylphenylamino)stilbene (2), and 4,4′-bis(di-4-tert-butylphenylamino)stilbene (3) were synthesized and characterized. To evaluate the electroluminescent properties of these compounds, multilayered OLED devices 1-3 were designed. By employing blue dopant 1 into a multilayer device, it was possible to achieve a maximum luminance of 8861 cd m−2 at 12.0 V, a luminous efficiency of 6.82 cd A−1 at 20 mA cm−2, a power efficiency of 2.72 lm W−1 at 20 mA cm−2, and CIE x,y coordinates of (x = 0.158,y = 0.187) at 10.0 V. These results demonstrated the superiority of these bis(diarylamino)stilbene derivatives in organic light-emitting devices.

Red Phosphorescent Iridium(III) Complexes Containing 5-Benzoyl-2-phenylpyridine Derived Ligands with Electron-Donating/-Withdrawing Moieties for Organic Light-Emitting Diodes

A series of red-phosphorescent Ir(III) complexes based on 5-benzoyl-2-phenylpyridine derivatives were synthesized. To explore their electroluminescent properties, multilayered OLEDs were fabricated the device structure of ITO/2-TNATA/NPB/Ir(III) complexes (8%) doped in CBP/BCP/Alq3/Liq/Al. The device 2 displays the excellent EL performances; its LE, PE, and EQE reach 30.4 cd/A, 10.1 lm/W, and 8.23% at 20 mA/cm2, respectively. The maximum electroluminescence spectrum peak was 571 nm, with the CIE coordinates of (0.486, 0.512) at 12.0 V, and the device also showed a stable color chromaticity with various voltages.

Synthesis and Electroluminescent Properties of Blue-Light-Emitting Arylene Derivatives End-Capped with Thiophene Groups

In this study, four blue fluorescent arylenes end-capped with thiophene derivatives have been synthesized. To explore electroluminescent properties of these molecules, multilayer OLEDs device structure of ITO/NPB/EML/BPhen/Al were fabricated. Two multilayer devices, using 3–4, showed the efficient deep blue emissions with CIE x,y of (0.159, 0.092) and (0.151,0.082) at 9.0 V, and the external quantum efficiencies of 1.60 and 0.80%, respectively. A PFVtPh doped-device exhibited the highly efficient blue emission with a maximum luminance of 3480 cd m−2 at 9.0 V, the external quantum efficiency of 5.23%, and CIE x,y of (0.151, 0.185) at 9.0 V.

Solution Processed Red Phosphorescent Organic Light-Emitting Diodes with Green Phosphorescent Ir Sensitizer

We fabricated the organic light-emitting diodes (OLEDs) with sensitizer by solution process. The addition of sensitizer into the emission layer improved the device efficiency. 4,4′-N,N′-dicarbazole-biphenyl (CBP), bis(2-phenylquinoline)iridium(III) (acetylacetonate) [Ir(pq)2(acac)], tris(2-phenylpyridine)iridium [Ir(ppy)3] were used as host, red emitting dopant, and sensitizer, respectively. The sensitizer leads to the cascade energy transfer from the host into the red emitting dopant. The doping concentration of sensitizer was varied as 0∼20 wt% and optimized. As a result, the device with 5% Ir(ppy)3 shows the luminous efficiency, power efficiency, and quantum efficiency of 5.1 cd/A, 4.0 lm/W, and 3.0%, respectively. These efficiencies are about 3 times as high as that of device without sensitizer.

Highly efficient organic light-emitting diodes based on the red phosphorescent emitter sensitized by the green emitting iridium complex

We demonstrated the red phosphorescent organic light-emitting diodes with sensitizer, iridium(III) tris(2-phenylpyridine) [Ir(ppy)<inf>3</inf>]. The devices with sensitizer showed a significant improvement in a luminance and efficiency compared to those without sensitizer. Moreover, the electroluminescent (EL) spectra of devices with sensitizer show a similar emission peak with photoluminescent (PL) spectra of iridium(III) bis(2-phenylquinoline)(acetylaceton) [Ir(pq)<inf>2</inf>(acac)] under the optimized doping ratio of Ir(pq)<inf>2</inf>(acac) and Ir(ppy)<inf>3</inf>. It is because that the triplet metal-to-ligand charge transfer (³MLCT) state of Ir(ppy)<inf>3</inf> is higher than that of Ir(pq)<inf>2</inf>(acac) and the intra-molecular energy transfer (IMET) time (within ns time scale) from the ppy-centered ³MLCT state to the pq-centered ³MLCT state is shorter than the radiative lifetime (within µs time scale) of Ir(ppy)<inf>3</inf>.

P‐163: Carbazole‐Isoquinoline Hybrid Bipolar Host Material for Highly Efficient Green Electrophosphorescent OLEDs

We synthesized and demonstrated electroluminescent properties of a bipolar host material such as 9-(3-(isoquinolin-1-yl)phenyl)-9H-carbazole (Czpiq). Particularly, by using Czpiq as a host and (bis[2-(1,1′,2′,1″-terphen-3-yl)pyridinato-C,N]iridium (III) (acetylacetonate) (tphpy)2Ir(acac) as a dopant, a green electrophosphorescent OLED was fabricated, showing a maximum power efficiency of 47.13 lm/W, maximum external quantum efficiency of 12.31%, and CIE x,y coordinates of (0.34, 0.58) at 8V.