Hayoon Lee

Synthesis and electroluminescence properties of highly efficient dual core chromophores with side groups for blue emission

Highly efficient blue emitting materials consisting of dual core derivatives with phenyl and/or naphthyl side groups and asymmetric or symmetric structures were designed and synthesized. The asymmetric structures 1-naphthalen-1-yl-6-(10-phenyl-anthracen-9-yl)-pyrene (Ph-AP-Na) and 1-(10-naphthalen-1-yl-anthracen-9-yl)-6-phenyl-pyrene (Na-AP-Ph), and the symmetric structures 1-phenyl-6-(10-phenyl-anthracen-9-yl)-pyrene (Ph-AP-Ph) and 1-naphthalen-1-yl-6-(10-naphthalen-1-yl-anthracen-9-yl)-pyrene (Na-AP-Na) were synthesized. Of the synthesized compounds, Na-AP-Na was found to exhibit the highest EL device efficiency of 5.46 cd A−1. Ph-AP-Na, Na-AP-Ph, Ph-AP-Ph, and Na-AP-Na exhibit EL maximum values of real blue color in the range 455 nm to 463 nm. The y values of their color coordinates are within the range 0.125 to 0.142, so these compounds exhibit good blue color coordinates for displays. The lifetime of the Na-AP-Na device was more than three times longer than that of the AP dual core (1-anthracen-9-yl-pyrene) device.

Synthesis and Property of New Blue Emitting Materials with Bulky Side Group

Two emitting compounds, 9,10-bis-[1,1′;3′,1′′]terphenyl-5′-yl-1,5-di-o-tolyl-anthracene [TP-DTA-TP] and 9,10-bis-phenyl[1,1′;3′,1′′]triphenyl-5′-yl-1,5-di-o-tolyl-anthracene [TPB-DTA-TPB] based on new twisted core moiety were synthesized through boration, Suzuki reaction, and Sandmeyer reactions. EL performance was improved by varying the chemical structure of the side group. Physical properties such as optical, electrochemical, and electroluminescent properties were investigated. Synthesized compounds were used as an EML in OLED device: ITO / 2-TNATA (60nm) / NPB (15nm)/ TP-DTA-TP or TPB-DTA-TPB (35 nm) / Alq3 (20nm) / LiF (1nm) / Al (200nm). It was found that TPB-DTA-TPB showed higher luminance efficiency and better C.I.E. value than TP-DTA-TP device.

New Emitting Materials Based on HTL Moiety with High Hole Mobility for OLEDs

New green emitting compounds based on tris(N-methylindolo)benzene (NMT), anthracene and pyrene were synthesized. NMT-An and NMT-Py were used as an emitting layer in OLED device to examine emitting property. OLED device containing NMT-An emitting layer and conventional hole transporting layer (HTL) of NPB was found to exhibit better characteristics compared to NMT-Py. And that device showed maximum EL emission at 502 nm and 550 nm, CIE coordinates (0.38, 0.48), and a luminance efficiency of 2.06 cd/A. Also when NMT and NMT-An were used as a HTL instead of NPB, the device including NMT-An emitter showed 2.67 cd/A and 2.29 cd/A in luminance efficiency.

Hybrid White Organic Light Emitting Diodes Using Dual Core Blue Fluorescent Emitter

White OLED (WOLED) devices were fabricated using blue emitting materials, TP-AA-TP, TP-AA-TPB, and TPB-AA-TPB, and yellow emitting material polyphenylenevinylene derivative (PDY 132). Three devices were fabricated with the following structure: ITO/PEDOT:PSS (50 nm)/PDY-132 (40 nm)/NPB (10 nm)/Blue EML (30 nm)/Alq₃ (20 nm)/LiF (1 nm)/Al (200 nm). PDY-132 was used by spin coating, and then three blue fluorescent materials were used by vapor deposition to form a white light emitting device. The color coordinates of WOLED using TP-AA-TP, TP-AA-TPB and TPB-AA-TPB were (0.291, 0.317), (0.317, 0.371) and (0.345, 0.457), respectively. Device using TP-AA-TP as blue emitting material showed the highest efficiencies at 10 mA/cm², L.E of 5.58 cd/A, P.E of 2.16 lm/W and E.Q.E of 2.96%.

Synthesis and property of diazocine derivatives substituted with imidazole in various positions

ABSTRACT TIACA-I, TIACA-II were synthesized by changing the substitution position of the imidazole group in the diazocine core. TIACA-I, TIACA-II in the film state showed absorption in the range of 354 to 392 nm and exhibited blue photoluminescence (PL) emissions at 448 and 462 nm, respectively. The PL wavelength of TIACA-II is red-shifted by 14 nm than that of TIACA-I due to the electron-donating intensity depending on the position of the imidazole group. The use of TIACA-II in a non-doped OLED device resulted in blue emission with current efficiency of 2.84 cd/A and CIE of (0.15, 0.18).

Synthesis of yellow synergist based on pigment yellow 74 for inkjet applications

ABSTRACT New yellow synergist was synthesized for pigment dispersion in pigment ink. 1,4-Butanesultone was applied to Pigment Yellow 74 (PY74) as a hydrophilic functional group in order to synthesize 4-[{2-[(2-Methoxy-4-nitro-phenyl)-(4-sulfo-butyl)-hydrazono]-1-methylene-3-oxo-butyl}-(2-methoxy-phenyl)-amino]-butane-1-sulfonic acid (PY74ASA-2). Whereas pigment showed extremely low solubility in water and organic solvents such as DMSO, DMF and methanol, the synergist was found to have higher solubility than pigment. This result can be interpreted as reduction of particle aggregation by increasing polarity. This synergist applied to pigment ink is expected to improve dispersion property and storage stability of ink.

Synthesis of new yellow synergists based on pigment yellow 150 for inkjet applications

ABSTRACT Inkjet technology using pigment requires pigment dispersity as well as the stability in solvents. New synergist PY-150ASA2 was synthesized by substituting 1,4-butane sultone in order to give the dispersity and the stability. The original pigments showed very low solubility in water and organic solvents. PY-150ASA2 has better solubility and stability in water compared to the pigment. Through the storage stability test, PY-150ASA2 disperses well in the pigment and has a smaller particle size than that of the solsperse 22000, a commercialized synergist. Synergest is expected to be applied to pigment inks for the improved performance.

Synthesis and Electroluminescence Properties of New Type Multi-Chromophore Emitting Materials for Organic Light-Emitting Diodes

New three emitting compounds, AK-1, AK-2 and AK-3 including diazocine moiety were synthesized through Suzuki-coupling reaction. Physical properties such as optical, electroluminescent properties were investigated. UV-visible spectrum of AK-1, AK-2 and AK-3 in film state showed maximum 392, 393 and 401 nm. PL spectrum of AK-1, AK-2 and AK-3 showed maximum emission wavelength of 472, 473 and 435 nm. Three compounds were used as EML in OLED device: ITO/2-TNATA (60 nm)/NPB (15 nm)/EML (35 nm)/Alq3 (20 nm)/LiF (1 nm)/Al (200 nm). AK-3 OLED device showed C.I.E value of (0.18, 0.26) and luminance efficiency of 0.51 cd/A at 10 mA/cm2. New derivatives including diazocine moiety were introduced as OLED emitting material and the EL efficiency was increased by the proper combination of core and side group.

Synthesis and Electroluminescence Properties of New Dual-Core Derivatives

New blue emitting materials based on dual core concept, TP-AF-TP and TP-HAF-TP were synthesized through boronylation and Suzuki coupling reactions. In the thin film state, TP-AF-TP and TP- HAF-TP exhibited maximum PL values at 445 and 440 nm, respectively. A non-doped OLED device based on TP-AF-TP and TP-HAF-TP showed current efficiency of 3.16 and 2.67 cd/A, respectively. TP-AF-TP exhibited a higher EL efficiency than that of TP-HAF-TP.

New Yellow Synergist for Stable Pigment Dispersion of Inkjet Ink

Minimizing ink droplet and self-dispersed pigment mixture are becoming hot issues for high resolution of inkjet printing. New synergist including sulfonic acid group of PY-74 was suggested and synthesized. Pigment itself did not show water solubility but new synergist, SY-11 exhibited good solubility in water and organic solvents such as DMSO and DMF. When aqueous pigment ink was prepared with SY-11, storage stability of the ink has been remained for 7 days under periodically repeated heating and cooling conditions. Particle size of formulated ink was around 150 nm.