• 한국정보디스플레이학회:학술대회논문집
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• 2006.08a
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• pp.1813-1818
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• 2006

We demonstrate a new approach to form gradient hole injection layer (HIL) in organic light-emitting diodes (OLEDs). Single spincoating of hole-injecting conducting polymer compositions with a perfluorinated ionomer results in gradient workfunction through the layer by self-organization, which lead to remarkably efficient single layer polymer light-emitting diodes (PLEDs) (${\sim}21$ cd/A). The device lifetime was significantly improved (${\sim50$ times) compared with the conventional hole injection layer, poly(3,4-ethylenedioxy-thiophene)/polystyrene sulfonate. This solution processed HIL also produced dramatically enhanced luminous efficiency (${\sim}34$ cd/A) in vacuum- deposited green fluorescent OLEDs while the vacuum deposited HIL gave the luminous efficiency of ${\sim}23$ cd/A in the same device structure.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07b
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• pp.1046-1049
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• 2004

The improvement in OLEDS performance is correlated with the surface chemical composition, hole injection and electron injection. In this study, a new hole injection material, HIL202(NPB derivatives), was synthesized and the devices with the structure of ITO/HIL202/NPB/$Alq_3$/Liq/Al were fabricated. The devices with a new hole injection material showed the improved current density, luminance and life time then the NPB or conventional hole injection material based OLEDs, due to the improved adhesion morphology between ITO surface and hole injection material.

• Journal of IKEEE
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• v.24 no.3
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• pp.706-712
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• 2020

To improve light-emitting performance of green phosphorescent organic light-emitting diodes (OLEDs), we introduced new hole injection materials-hexaazatrinaphthylene (HATNA) derivatives as a solution processed hole injection layer (HIL). The HATNA derivative has a low the lowest unoccupied molecular orbital (LUMO) energy level, similar to the work function of Indium Tin Oxide (ITO), showing a different concept of hole injection mechanism. It was confirmed that the device efficiency of OLEDs using HATNA-HIL showed the improved external quantum efficiency from 10.8% to 15.6% and current efficiency from 32.7 cd/A to 42.7 cd/A due to the balance of electrons and holes in the emissive layer.

• 한국정보디스플레이학회:학술대회논문집
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• 2005.07b
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• pp.1619-1622
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• 2005

The ultra thin hole injection layer (HIL) was deposited on an indium-tin-oxide (ITO) anode by using an ion beam assisted d eposition (IBAD) for the fabrication of an polymeric electroluminescence device for the first time. The device with the HIL deposited by IBAD has higher external quantum efficiency than the device with the HIL by conventional thermal evaporation. It is found that the deposited HIL by IBAD has high surface coverage on ITO anode in a few nm regions because the HIL prepared has high adatom mobility by ion beam energy.

• 한국정보디스플레이학회:학술대회논문집
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• 2009.10a
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• pp.781-783
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• 2009

We achieved high efficiency and long lifetime in small-molecule organic light-emitting diodes using a blend of polyaniline-based conducting polymer and a perfluorinated ionomer as a hole injection layer (HIL). The HIL formed by single spin coating greatly enhanced the surface work function and thus the hole injection from the anode, which resulted in great improvement in device luminous efficiency. We find that the solution processed HIL outperforms the conventional vacuum-deposited small molecule HIL in terms of the device performance.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.21 no.6
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• pp.562-568
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• 2008

In this paper, the hole injection layer(HIL) materials have been synthesized and analyzed. Their HOMO levels are $4.93{\sim}5.22\;eV$, and their energy band gaps are $2.74{\sim}3.19\;eV$. Their glass transition temperatures($T_g$) are all above $114^{\circ}C$, which implies that they are highly thermal-stable. The green OLED devices with a structure of ITO(150 nm)/NEW_HIL(50 nm)/NPB(30 nm)/$Alq_3$(50 nm)/Al:Li(100 nm) were fabricated and tested, incorporating these newly synthesized HIL materials. According to the test results of OLED devices, the I-V-L performances of these devices increase in the following sequence: ELM307 > ELM200 > ELM321 > ELM327 > ELM325. In addition, the OLED device with ELM307 as a HIL has the highest brightness and efficiency at the same driving voltage. These experimental results have shown that ELM307 can be used as one of the most promising candidates for HIL materials.

• 한국정보디스플레이학회:학술대회논문집
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• 2009.10a
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• pp.354-355
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• 2009

In the fabrication of inverted top-emitting organic light emitting diodes (ITOLEDs), the sputtering process is needed for deposition of transparent conducting oxide (TCO) as top anode. Energetic particle bombardment, however, changes the physical properties of underlying layers. In this study, we examined plasma process effects on tungsten oxide ($WO_3$) hole injection layer (HIL). From our results, we suggest the theoretical mechanism to explain the correlation between the physical property changes caused by plasma process on $WO_3$ HIL and degradation of device performances.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.26 no.12
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• pp.899-903
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• 2013

We investigated the luminescence properties of $Alq_3$ in the device structure of ITO/CuPc/TPD/$Alq_3$/Al. The CuPc as a hole-injection material and TPD as hole-transport material. Emission properties were measured by varying a layer thickness of CuPc (0 nm to 50 nm), which is the hole-injection layer. As a result, it was found that the hole injection occurs smoothly when the layer thickness was 20 nm among the thicknesses from 0 nm to 50 nm.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.27 no.1
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• pp.50-55
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• 2014

It was firstly found in 1st group element. Recently, it has been reported on the improvement of efficiency of the OLEDs by introducing thin layer of some carbonate materials of alkali metal. In order to improve the efficiency of OLEDs which is one of the next generation displays, we have studied the electrical characteristics of the device depending on the thickness ratio of the hole-injection layer to the electron-injection layer. Teflon-AF was used as the hole-injection material, and alkali-metal carbonates of $Li_2CO_3$ were used as the electron-injection materials. To obtain a proper thickness ratio, we manufactured. Four types of devices with the thickness ratio of HIL to EIL were made to be 1 : 4, 2 : 3, 3 : 2, and 4 : 1. The results of electrical and optical properties showed that the device with the thickness ratio of 4 : 1 is the most excellent result. In addition, to prepare a four-layer device by inserting the ${\alpha}$-NPD is a hole transporting material was compared with three-layer element. As a result, the maximum luminance, the maximum luminous efficiency, maximum external quantum efficiency of about 124 [%], 164 [%], 106 [%] improve was confirmed.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.305-306
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• 2009

In this study, we have invastigated the recombination zone in the blue phosphorescent organic light-emitting devices with various partially doped structures. The basic device structure of the blue PHOLED was anode / hole injection layer (HIL) / hole transport layer (HTL) / emittingvastigated the recombination zone in the blue layer (EML) / hole blocking layer (HBL) / electron transport layer (ETL) / electron injection layer (EIL) / cathode. After the preparation of the blue PHOLED, the current density (J) - voltage (V) - luminance (L) and current efficiency characteristics were measured.