• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.1511-1513
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• 2005

The polymer-light emtting diodes(PLEDs) were comprised a design of OLED array, process develop by using ITO thin glass, and fabrication of PDMS stamp by using nanocontact printing. In the study, we describe a different approach for building OLEDs, which is based on physical lamination of thin metal electrodes supported by a PDMS stamp layer against an electroluminescent organic. We develop that devices fabricated in this manner have better performance than those constructed with standard processing techniques. The lamination approach avoids forms of disruption that can be introduced at the electrode organic interface by metal evaporation and has a reduced sensitivity to pinhole or partial pinhole defects. Also, it is easy to build patterned PLED with feature sizes into the nanometer regime. This method provides a new route to PLED for applications ranging from high performance displays to storage and lithography systems, and PLED can used for organic electronics and flexible display.

• Journal of the Optical Society of Korea
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• v.17 no.3
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• pp.269-274
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• 2013

The effect of diffusing substrate and pillow lenses on the outcoupling efficiency of organic light-emitting diodes (OLEDs) was studied by optical simulation based on the point-dipole model. The diffusing substrate included Mie scatterers by which the condition of total internal reflection could be broken. The finite-difference time-domain method was used to obtain the intensity distribution on the transparent electrode of an OLED, which was used as a light source to carry out a ray-tracing simulation of the OLED and the diffusing substrate. It was found that the outcoupling efficiency of the OLED was sensitive to the thickness of organic layers and could be increased by 21.0% by adopting a diffusing substrate in which Mie scatterers whose radius was $2.0{\mu}m$ were included at the density of $10^7mm^{-3}$ and by 65.5% by forming one pillow lens with the radius of 2 mm on the front surface of the glass substrate. This study revealed that the outcoupling efficiency could be improved by adopting diffusing substrate and pillow lenses along with the optimization of the thickness of each layer in the OLED.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.11a
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• pp.275-276
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• 2005

Organic Light Emitting Diodes(OLEDs) are attractive as alternative display components because of their relative merits of being self-emitting, having large intrinsic viewing angle and fast switching speed. But because of their relatively short history of development, much remains to be studied in terms of their basic device physics and design, manufacturing techniques, stability and so on. We invested electrical properties of N,N-diphenyl-N,N bis (3-methyphenyl)-1,1'-biphenyl-4,4'-diamine(TPD) and tris-8-hydroxyquinoline aluminum($Alq_3$) when their thicknesses were changed variedly from 3:7 to 7:3 of their thickness ratios. And we also studied properties of OLEDs depend on their deposition rate between 0.05$\sim$0.2 [nm/s].

• 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.

• 한국정보디스플레이학회:학술대회논문집
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• 2008.10a
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• pp.185-188
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• 2008

We have analyzed the structures of $Alq_3$ in different polymorphs by solid-state NMR. On the basis of the results, OLEDs were fabricated from different polymorphs of $Alq_3$. The current efficiency of the device fabricated from the mixture of $\alpha$-, $\gamma$-, and $\delta-Alq_3$ powders was higher than that from $\alpha-Alq_3$.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.111.2-111.2
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• 2015

Typical electrodes (metal or indium tin oxide (ITO)), which were used in conventional organic light emitting devices (OLEDs) structure, have transparency and conductivity, but, it is not suitable as the electrode of the flexible OLEDs (f-OLEDs) due to its brittle property. Although Graphene is the most well-known alternative material for conventional electrode because of present electrode properties as well as flexibility, its carrier injection barrier is comparatively high to use as electrode. In this work, we performed plasma treatment on the graphene surface and alkali metal doping in the organic materials to study for its possibility as anode and cathode, respectively. By using Ultraviolet Photoemission Spectroscopy (UPS), we investigated the interfaces of modified graphene. The plasma treatment is generated by various gas types such as O2 and Ar, to increase the work function of the graphene film. Also, for co-deposition of organic film to do alkali metal doping, we used three different organic materials which are BMPYPB (1,3-Bis(3,5-di-pyrid-3-yl-phenyl)benzene), TMPYPB (1,3,5-Tri[(3-pyridyl)-phen-3-yl]benzene), and 3TPYMB (Tris(2,4,6-trimethyl-3-(pyridin-3-yl)phenyl)borane)). They are well known for ETL materials in OLEDs. From these results, we found that graphene work function can be tuned to overcome the weakness of graphene induced carrier injection barrier, when the interface was treated with plasma (alkali metal) through the value of hole (electron) injection barrier is reduced about 1 eV.

• 한국정보디스플레이학회:학술대회논문집
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• 2008.10a
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• pp.446-449
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• 2008

Organic light emitting diodes (OLEDs) with multiple organic layers were fabricated to obtain and to evaluate an equivalent resistance and an equivalent capacitance of OLED device. The staircase voltage with an increasing period and a constant period was designed and applied to the OLED. The resistance of OLED was found to decrease from $270\;k{\Omega}$ to $2\;K{\Omega}$ as applied voltage increased after turn on. The equivalent capacitance of OLED maintained unchanged at low voltage level and deceased after showing peak value as the applied voltage increased.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.21 no.9
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• pp.859-862
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• 2008

We have realized static image on organic light emitting diodes (OLEDs) using photoluminescence degradation. Ultraviolet (UV) was irradiated to the glass side of device. UV power was 350 Wand the wavelength was 365 nm. The UV irradiation gives rise to the degradation of photoluminescence. Due to the degradation, the current density-voltage curve was shifted to the higher voltage side and the luminescence was also degraded by the current and photoluminescence drop. The negative imaged films were prepared to control the transmittance of UV. The UV light was passed through the film. By this method, the film image was transferred to the device with reversed image and the static image was realized on the OLED.

• Applied Chemistry for Engineering
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• v.34 no.1
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• pp.94-97
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• 2023

2,7-bis(3',6'-diphenyl-[1,1':2',1"-terphenyl]-4'-yl)-9,9'-spirobi[fluorene] (BTPSF) and 2,7-bis(1,4-diphenyltriphenylen-2-yl)-9,9'-spirobi[fluorene] (BDTSF) were successfully synthesized as novel blue-emission materials for organic light-emitting diodes (OLEDs) based on the spirobifluorene (SBF) moiety. BTPSF and BDTSF were obtained in high purity via a Diels-Alder reaction, without the use of a catalyst. Photoluminescence spectra of the synthesized materials showed maximum emitting wave-lengths of approximately 381 and 407 nm in solution and 395 and 434 nm in the film state, for BTPSF and BDTSF, respectively, indicating ultra-violet and deep blue emission colors. BDTSF was applied as an emissive layer (EML) in non-doped devices and achieved a current efficiency of 0.61 cd/A and an external quantum efficiency (EQE) of 0.46%.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.18 no.12
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• pp.1139-1142
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• 2005

Recently, organic light emitting diodes(OLEDs) is widely used as one of the information display techniques. We synthesized 2-(2-hydroxyphenyl)benzoxazole($Zn(HPB)_2$). We studied the luminescent properties of OLEDs using $Zn(HPB)_2$. The ionization potential(IP) and the electron affinity(EA) of $Zn(HPB)_2$ investigated using cyclic-voltammetry(C-V). The IP and EA were 6.5 eV and 3.0 eV, respectively. The PL and EL spectra of $Zn(HPB)_2$ were observed at the wavelength of 450 nm. We used $Zn(HPB)_2$ as an emitting layer and hole blocking layer. At the experiment about hole blocking effect, we inserted $Zn(HPB)_2$ between emiting material layer(EML) and cathode, and between hole transport layer(HTL) and emitting material layer(EML). We measured current density-voltage and luminance-voltage characteristics at room temperature.