Hwangyu Shin

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.

Recent progress in the use of fluorescent and phosphorescent organic compounds for organic light-emitting diode lighting

Abstract. Organic light-emitting diodes (OLEDs) have attracted considerable attention in both academic and industrial circles. Certain properties of OLEDs make them especially attractive in the lighting market, including area emission characteristics not found in other existing light sources, environmentally friendly efficient use of energy, large area, ultra-light weight, and ultra-thin shape. Fluorescent and phosphorescent materials that are being applied to white OLEDs have been categorized, and the chemical structures and device performances of the important blue, orange, and red light-emitting materials have been summarized. Such a systematic classification and understanding of the materials that have already been reported can aid the development and study of new light-emitting materials through quantitative and qualitative approaches.

Excimer emission based on the control of molecular structure and intermolecular interactions

Three triple-core chromophore derivatives based on anthracene and pyrene or chrysene moieties, 1,6-bis-(10-[1,1′;3′,1′′]terphenyl-5′-yl-anthracen-9-yl)-pyrene (1,6 DAP-TP), 6,12-bis-(10-[1,1′;3′,1′′]terphenyl-5′-yl-anthracen-9-yl)-chrysene (DAC-TP), and 2,7-bis-(10-[1,1′;3′,1′′]terphenyl-5′-yl-anthracen-9-yl)-pyrene (2,7 DAP-TP), were designed and synthesized. For 1,6 DAP-TP, anthracene was attached to the 1,6 positions of pyrene. In the case of DAC-TP, two anthracenes were connected to chrysene, located at the center position within the core, whereas in 2,7 DAP-TP anthracene was connected to the 2,7 positions of pyrene. All three materials had highly twisted core structures and bulky m-terphenyl side groups introduced into the core. Excimer emission was observed in the solid film state and can be interpreted as the result of anisotropic intermolecular alignment (orientation effect). The wavelength of excimer formation was controlled through the change of the center position of the triple-core chromophore, and the color coordinate of white light and efficiency could be controlled when the materials were used in an electroluminescence (EL) device. Excimer EL emissions of 1,6 DAP-TP, DAC-TP, and 2,7 DAP-TP were at 591 nm, 556 nm, and 538 nm, respectively, and CIE coordinate values of the devices were (0.37, 0.31), (0.30, 0.37), and (0.32, 0.44), respectively, showing single molecular white emission. 2,7 DAP-TP showed a white OLED efficiency of 6.01 cd A−1 at 10 mA cm−2.

Assessing migraine disability by diary-based measurement: relationship to the characteristics of individual headache attacks

Background and purpose:  Information on headache‐related disability helps clinicians create the optimal treatment plan for migraine sufferers. The estimation of disability must be determined by gathering the individual effects of multiple headache attacks within a given period of time. This study was aimed to examine migraine‐related disability from diary‐based assessment and to determine which elements of the headache characteristics are associated with disability.

New asymmetrical limb structured blue emitting material for OLED [Invited]

New asymmetric limb-structured blue light emitting material, composed of anthracene main core, naphthalene units at 9,10-position of anthracene and m-(di(trifluoromethylphenyl)) units at 2,3-positon of anthracene was designed and developed. And non-doped organic light-emitting diodes have been realized. The maximum efficiency of 1.72 cd/A and the quantum efficiency was around 0.67%.

Synthesis and electroluminescence property of new hexaphenylbenzene derivatives including amine group for blue emitters.

Three new blue-emitting compounds of 5P-VA, 5P-VTPA, and 5P-DVTPA for organic light-emitting diode (OLED) based on hexaphenylbenzene moiety were demonstrated. Physical properties by the change of the substitution groups of the synthesized materials were systematically examined. Photoluminescence spectrum of the synthesized materials showed maximum emitting wavelengths of about 400 to 447 nm in solution state and 451 to 461 nm in film state, indicating deep blue emission color. OLED devices were fabricated by the synthesized compounds using vacuum deposit process as an emitting layer. The device structure was ITO/2-TNATA 60 nm/ NPB 15 nm/ EML 35 nm/ TPBi 20 nm/ LiF 1 nm/ Al 200 nm. External quantum efficiencies and CIE values of 5P-VA, 5P-VTPA, and 5P-DVTPA were 1.89%, 3.59%, 3.34%, and (0.154, 0.196), (0.150, 0.076), (0.148, 0.120), respectively. 5P-VTPA and 5P-DVTPA exhibited superior highly blue quality and thermal property such as high Td of 448°C and 449°C.

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.

Synthesis and characterization of titanium complex with a dithiolate ligand for green LCD color filter dyes

Three green compounds for color filter dyes based on bis(cyclopentadienyl) titanium complexes including dithiolate ligand were synthesized. Physical properties by the change of the substitution groups of the synthesized materials were systematically examined. UV-visible absorption spectrum of the synthesized materials showed maximum absorbing wavelengths of 427 to 430 nm and 632 to 635 nm in solution state, and 434 to 438 nm and 637 to 651 nm in film state, indicating green and black colors. It was observed that the extinction coefficient values (log ε) of all the synthesized materials are very high at 4.0 or above. In addition, it was shown that since the Td values of three synthesized materials show thermal stability higher than 240°C, they possess high potential to be applied as dyes for LCD color filter and black matrix addictive.

Achieving a high-efficiency dual-core chromophore for emission of blue light by testing different side groups and substitution positions

Hetero dual-core derivatives that combine anthracene and pyrene were systematically studied for the purpose of producing highly efficient blue light-emitting materials applicable to organic light-emitting diode (OLED) lighting. Five compounds were designed in order to (1) determine which one of the two core chromophores in a hetero dual-core moiety, if any, acts as the main contributor to the optical and electronic properties of the final compounds, (2) control the electron-donating ability of the side group, and (3) change the substitution position. 1-[1,1′;3′,1′′]terphenyl-5′-yl-6-(10-[1,1′;3′,1′′]terphenyl-5′-yl-anthracen-9-yl)-pyrene (TP-AP-TP) was used as the reference material, and four other materials, including diphenyl-[10-(6-[1,1′;3′,1′′]terphenyl-5′-yl-pyren-1-yl)-anthracen-9-yl]-amine (DPA-AP-TP), diphenyl-[6-(10-[1,1′;3′,1′′]terphenyl-5′-yl-anthracen-9-yl)-pyren-1-yl]-amine (TP-AP-DPA), diphenyl-{4-[10-(6-[1,1′;3′,1′′]-terphenyl-5′-yl-pyren-1-yl)-anthracen-9-yl]-phenyl}-amine (TPA-AP-TP) and diphenyl-{4-[6-(10-[1,1′;3′,1′′]terphenyl-5′-yl-anthracen-9-yl)-pyren-1-yl]-phenyl}-amine (TP-AP-TPA), were synthesized as model compounds. The synthesized materials showed absorption wavelength peaks at 403–410 nm in the film state and exhibited PL emissions of 458–505 nm. Also, anthracene was shown to be the main core contributing to the optical and electronic properties. Among the synthesized molecules, the TPA-AP-TP molecule, in which triphenylamine, with its optimum electron-donating ability, was substituted into anthracene, showed excellent electroluminescence (EL) performance for OLED lighting with a current efficiency of 8.05 cd A−1, external quantum efficiency of 6.75%, and narrow EL FWHM of 53 nm.

White emission based on excimer emission control of triple core chromophores

Three materials had highly twisted molecular structures. In film state, excimer emission can be interpreted as result of orientation effect. Wavelength of excimer was controlled through the change of center position of triple core chromophore, and the CIE of white light could be controlled.