• Journal of the Semiconductor & Display Technology
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• v.18 no.4
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• pp.69-74
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• 2019

The aim of this work is to investigate the effect of the microtip length in a slot-die head on coating of a fine poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS) stripe. To this end, we have employed a meniscus guide with a 150-㎛-wide microtip and performed roll-to-roll slot-die coatings by varying its length between 500 ㎛ and 50 ㎛. When the microtip length is 150 ㎛ or shorter, we have observed three unexpected phenomena; 1) though the solution spreads much wider than the microtip width, yet the coated stripe width is almost the same as the microtip width, 2) the stripe width decreases, but the stripe thickness is rather increased with increasing coating speed at a fixed flow rate, 3) we obtain stripes much narrower than the microtip width at high coating speeds. It is due to the fact that 1) the meniscus is not well controlled by a short microtip, 2) the main stream of solution from the outlet is very close to the substrate and thus the distributed solution along the head lip merges with the main stream, and 3) the solution is not spread over the entire microtip end at high coating speeds, causing a tiny wobble in the meniscus. Using the 150-㎛-wide and 250-㎛-long microtip, we have fabricated 153-㎛-wide and 94-nm-thick PEDOT:PSS stripe at the maximum coating speed of 13 mm/s. To demonstrate its applicability in solution-processable organic light-emitting diodes (OLEDs), we have also fabricated an OLED device with the fine PEDOT:PSS stripe and obtained strong light emission from it.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.27 no.5
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• pp.307-311
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• 2014

Because of a waveguiding effect and total internal reflection caused by a difference in refractive indices, only 20% of generated light is emitted to the air and the rest is trapped or absorbed in the device. An improvement of outcoupled efficiency of organic light-emitting diodes was studied using a microlens array. Mold of microlens array was fabricated by using photo-lithography with the AZ9260 photoresist, and the microlens array was formed onto the glass substrate using the UV curing agent named ZPU13-440. Device structure consists of microlens/glass/ITO/TPD/$Alq_3$/LiF/Al. It was found that there is an improvement of external quantum efficiency by about 20% at the same current density for the device with the microlens array compared to that of the reference one. Simulated outcoupled efficiency shows the improvement by about 20% for the device with the microlens array compared to that of the reference one. These results are consistent with the experimental ones.

• Bulletin of the Korean Chemical Society
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• v.35 no.6
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• pp.1639-1646
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• 2014

A series of novel fused-ring spiro compounds, spiro[benzo[ij]tetraphene-7,9'-fluorene] (SBTF) derivatives containing an end-capping aryl substituent at both the C3 and C10-positions hasbeen designed and synthesized via multi-step Suzuki coupling reactions. 3-(1-Naphthyl)-10-phenylSBTF (1N-PSBTF), 3-(2-naphthyl)-10-phenylSBTF (2N-PSBTF) and 3-[4-(1-naphthyl)phenyl]-10-phenylSBTF (NP-PSBTF) showed improved glass transition temperatures ($T_g$) with good thermal stability. Their photophysical, electrochemical, and electroluminescent properties were investigated and were used to construct blue organic light emission diodes (OLEDs). The typical OLED devices showed excellent performance; the NP-PSBTF-based device exhibited highly efficient deep blue-light emission with a maximum efficiency of 5.27 cd/A (EQE, 4.63%) with CIE (x = 0.133, y = 0.144). According to these characteristics, these deep-blue light emitting materials have sufficient potential for fluorescent OLED applications.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.1373-1374
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• 2007

We has been synthesized $(POB)_{2}Ir(pic)$ as a red emitting materials and evaluated in the organic light emitting diodes (OLED). The layer of $Alq_3$ doped with $(POB)_{2}Ir(pic)$ as emitters has been demonstrated. The structure of the device is ITO/ NPB (40 nm) / $Zn(HPB)_2$ (40 nm)/ $Alq_3$ : $(POB)_{2}Ir(pic)$ (30 nm) / LiF / Al. We varied the doped rate of $(POB)_{2}Ir(pic)$. The doped rate is 0.4 %, 0.6%, 0.8 and 1.2%, respectively. When the doped rate of the $Alq_3$:$ Ir(POB)_{2}(pic)$ was 0.6%, white emission is achieved. The Commission Internationale de l'Eclairage (CIE) coordinates of the white emission are (0.316, 0.331) at an applied voltage of 10.75V.

• Journal of Information Display
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• v.11 no.1
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• pp.1-7
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• 2010

The intermediate connectors play crucial roles in the performance of tandem organic light-emitting diodes (OLEDs) because they are required to facilitate charge carrier transport and to guarantee transparency for light transmission and deposition compatibility. Understanding the physical properties of the intermediate connector is not only fundamentally important but is also crucial to developing high-efficiency organic devices with a tandem structure. In this study, several effective intermediate connectors in tandem OLEDs using a doped or non-doped organic p-n heterojunction were systematically investigated by studying their interfacial electronic structures and corresponding device characteristics. The working mechanisms of the intermediate connectors are discussed herein by referring to their relevant energy levels with respect to those of the neighboring organic layers. The factors affecting the operation of the intermediate connectors in tandem OLEDs, as demonstrated herein, provide guidance for the identification of new materials and device architectures for high-performance devices.

• Journal of the Microelectronics and Packaging Society
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• v.15 no.2
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• pp.1-6
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• 2008

New devices with the structure of ITO/2-TNATA/NPB/TCTA/CBP:$7%Ir(ppy)_3$/BCP/SFC-137/LiF/Al were designed and fabricated to develop high efficiency green phosphorescent organic light emitting diodes and their electroluminescence properties were evaluated. Among the devices with different thicknesses of CBP in a range of $150{\AA}{\sim}350{\AA}$, the best luminance was obtained in the device with $300{\AA}$-thick CBP host. Nearly saturated current efficiencies indicates that the maximum efficiency value can be obtained with CBP thicknesses of $300{\AA}{\sim}350{\AA}$. The current density, luminance, and current efficiency of the PhOLED(phosphorescent organic light emitting diode) with $CBP(300{\AA}):7%Ir(ppy)_3-emissive$ layer at an applied voltage of 10V were $40mA/cm^2,\;10000cd/m^2$, and 25 cd/A, respectively. The maximum current efficiency was 40.5cd/A under the luminance of $160cd/m^2$. The peak wavelength and FWHM(full width at half maximum) in the electroluminescence spectral were 512nm and 60nm, respectively. The color coordinate was (0.28, 0.63) on the CIE (Commission Internationale de I'Eclairage) chart.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.11a
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• pp.320-321
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• 2006

In this work, impedance Spectroscopic analysis was applied to study the effect of plasma treatment on the surface of indium-tin oxide (ITO) anodes using $CF_4g$ as and to model the equivalent circuit for organic light emitting diodes (OLEDs) with the $CF_4$ plasma treatment of ITO surface at the anodes. This device with ITO/TPD/$Alq_3$/LiF/Al structure can be modeled as a simple combination of a resistor and a capacitor. The $CF_4$ plasma treatment on the surface of ITO shifts the vacuum level of the ITO as a result of which the barrier height for hole injection at the ITO/organic interface is reduced. The Impedance spectroscopy measurement of the devices with the $CF_4$ plasma treatment on the surface of ITO anodes shows change of values in parallel resistance ($R_p$) and parallel capacitance ($C_p$).

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.436-437
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• 2006

In this work, impedance Spectroscopic analysis was applied to study the effect of plasma treatment on the surface of indum-tin oxide (ITO) anodes using $O_2$ gas and to model the equivalent circuit for organic light emitting diodes (OLEDs) with the $O_2$ plasma treatment of ITO surface at the anodes. This device with ITO/TPD/Alq3/LiF/Al structure can be modeled as a simple combination of a resistor and a capacitor. The $O_2$ plasma treatment on the surface of ITO shifts the vacuum level of the ITO as a result of which the barrier height for hole injection at the ITO/organic interface is reduced. The impedance spectroscopy measurement of the devices with the $O_2$ plasma treatment on the surface of ITO anodes shows change of values in parallel resistance ($R_p$) and parallel capacitance ($C_p$).

• Journal of the Korean Applied Science and Technology
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• v.34 no.3
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• pp.562-567
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• 2017

The organic light-emitting diodes are fabricated with six anthracene derivatives containing simple substituents such as phenyl or naphthyl group. The device structure is as in the following: Indium tin oxide (ITO) (180 nm)/4,4-4,4',4"-tris[N-(1-naphthyl)-N-phenylamino]triphenylamine (2-TNATA) (30 nm)/4,4'-bis[N-(1-naphthyl)-N-phenyl-1-amino] biphenyl (NPB) (20 nm)/Emitting compound (30 nm)/2,2',2"-(1,3,5-Benzinetriyl)-tris (1-phenyl-1-H-benz-imidazole) TPBi (40 nm)/lithium quinolate (Liq) (2 nm)/Al (100 nm). In the emitting layer the anthracene derivatives are used without any dopant. All the six devices show blue emissions. Among the tested diodes, the one with 9-(2-naphthyl)-10-(p-tolyl) anthracene (2-NTA) exhibited luminous efficiency, power and external quantum efficiencies of 3.26 cd/A, 0.98 lm/A, 2.8 % at $20mA/cm^2$.

• Bulletin of the Korean Chemical Society
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• v.27 no.10
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• pp.1549-1552
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• 2006

We report a new series of blue dopants composed of both electron donating and electron accepting moieties in one molecule, based on nalidixic acid. The EL device derived from the dopant exhibits pure blue light emission (0.15, 0.14) The current efficiency is estimated to be 3.88 cd/A at 100 $cd/m^2$, which shows remarkable enhancement, compared to that of the host itself (2.5 cd/A at 100 $cd/m^2$) under the same conditions. These results demonstrate that the incorporation of a proper guest into the host in a guest-host doped system improves not only the purity of the fluorescent blue emission but also elevates its quantum efficiency, thus improving the OLED performance.