• Journal of the Korean institute of surface engineering
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• v.41 no.5
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• pp.199-204
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• 2008

Indium tin oxide (ITO) has been commonly used as an anode for organic light emitting diode (OLED), because of its relatively high work function, high transmittance, and low resistance. The ITO was mostly deposited by capacitive type DC or RF sputtering. In this study we introduced a new facing target sputtering method. On applying this new sputtering method, the effect of fundamental deposition parameters such as substrate heating and post etching were investigated in relation to the resultant I-V-L characteristics of OLED. Three kinds of ITOs deposited at room temperature, at $400^{\circ}C$ and at $400^{\circ}C$ with after surface modification by $O_2$ plasma etching were compared. The OLED on ITO deposited with substrate heating and followed by etching showed better I-V-L characteristics, which starts to emit light at 4 volts and has luminescence of $65\;cd/m^2$ at 9 volts. The better I-V-L characteristics were ascribed to the relevant surface roughness with uniform micro-extrusions and to the equi-axed micromorphology of ITO surface.

• Proceedings of the Materials Research Society of Korea Conference
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• 2009.05a
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• pp.36.1-36.1
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• 2009

OLED(organic light emitting diode)는 차세대 평판 디스플레이로 전자종이, 입는 디스플레이 등 flexible한 디스플레이로도 주목받고 있다. 하지만, OLED의 가장 큰 단점 중의 하나가 수분과 산소에 매우 민감하다는 것으로 이것은 OLED의 lifetime과 연결된다. 따라서 이에 대한 mechanism의 확립이 필요하다. 따라서 본 연구에서는, flexible한 OLED에 적용되는 금속 코팅막의 적층구조 및 기판의 노출온도에 따른 금속 코팅막의 수분침투 특성에 대해 MOCON의 weight gain test (WGT)를 통해 barrier layer에 대해 평가하고 이에 대한 mechanism을 확립하는데 그 목적이 있다. 금속 코팅막은 OLED의 cathode와 anode 재료로 많이 사용되는 Al과 ITO를 sputter장비를 이용해 single layer와 multi-layer의 두 가지 구조로 PET기판에 증착하였다. 또한, 노출온도에 따른 특성을 알아보고자 bare PET / ITO coated PET(single layer $50{\mu}m$) / Al coated PET(single layer $200{\mu}m$)의 세 가지 시편을 제작하였다. 이 시편을 각각 $25^{\circ}C$, $37.8^{\circ}C$, $50^{\circ}C$의 온도에서 test를 진행하였고 이 과정을 100%RH, 70%RH, 40%RH조건의 수분조건에서 진행하여 각각의 수분조건에서 각각의 온도에 따른 금속 코팅막의 수분침투 특성에 대한 mechanism을 확립하였다. 적층구조에 따른 수분침투 특성 평가 결과 multi-layer가 single layer보다 더 우수한 수분침투의 barrier 특성을 나타냈었다. 그리고 각 온도에 따른 test결과 온도가 증가할수록 barrier의 특성이 나빠짐이 보였다.

• Journal of the Korean institute of surface engineering
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• v.48 no.3
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• pp.105-109
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• 2015

We studied emission characteristics of blue fluorescent multi-tandem OLEDs using $Al/MoO_x$ as charge generation layer(CGL). Threshold voltage for 2, 3, 4, and 5 units tandem OLEDs was 8, 11, 14 and 18 V, respectively. The threshold voltage in multi-tandem OLEDs was lower than multiple of 4 V for the single OLED. Maximum current efficiency and maximum quantum efficiency of single OLED were 7.6 cd/A and 5.5%. Maximum current efficiency for 2, 3, 4, and 5 units tandem OLEDs was 22.6, 31.4, 41.2, and 46.6 cd/A, respectively. Maximum quantum efficiency for 2, 3, 4, and 5 units tandem OLEDs was 11.8, 15.8, 21.8, and 25.6%, respectively. The maximum current efficiency and maximum quantum efficiency in multi-tandem OLEDs were higher than multiple of those for the single OLED. The intensity for 508 nm peak was changed and the peak wavelength was red shift by increase of tandem unit in electroluminescent emission spectra. These phenomena can be caused by micro-cavity effect with increasing of organic layer thickness.

• 한국정보디스플레이학회:학술대회논문집
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• 2009.10a
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• pp.758-761
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• 2009

The electroluminescent devices with the phenylnaphthyldiamine HTMs as the hole-transporting layer were more efficient than that with the biphenyldiamine HTM 1. Particularly, the life-time of the device IV using HTM 2 is about two times longer than that of the reference device III with HTM 1 within the measured current density, indicating more effective recombination at the emitting layer of device IV.

• Journal of the Semiconductor & Display Technology
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• v.20 no.4
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• pp.141-145
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• 2021

The brightness of the Organic Light Emitting Diode (OLED) display is controlled by thin-film transistors (TFTs). Regardless of the materials and the structures of TFTs, an OLED suffers from the instable threshold voltage (V_th) of a TFT during operation. When designing an OLED pixel with circuit simulation tool such as SPICE, a designer needs to take V_th shift into account to improve the reliability of the circuit and various compensation methods have been proposed. In this paper, the effect of the compensation circuits from two typical OLED pixel circuits proposed in the literature are studied by the transient simulation with a SPICE tool in which the stretched-exponential time dependent V_th shift function is implemented. The simulation results show that the compensation circuits improve the reliability at the beginning of each frame, but V_th shifts from all TFTs in a pixel need to be considered to improve long-time reliability.

• Journal of the Korean institute of surface engineering
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• v.47 no.3
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• pp.99-103
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• 2014

The encapsulation method of flexible organic light emitting devices (OLEDs) was investigated for the structure of ITO / 2-TNATA / NPB / $Alq_3$ : Rubrene (1 vol.%) / $Alq_3$ / LiF / Al / $Alq_3$ / LiF / Al (OLED #1), on which $SiN_x$ thin film was deposited and metal film was attached to protect the damage of OLED from oxygen and moisture. The $SiN_x$ thin film was deposited by plasma enhanced chemical vapor deposition (PECVD) method using $SiH_4$ of 20 sccm and $N_2$ of 15~35 sccm as reactor gases. The optimum $SiN_x$ deposition condition was found to be 20 sccm $SiH_4$ and 20 sccm $N_2$ from the Ca test of the fabricated $SiN_x$ thin film. The life time of OLED #1, OLED #1 / $SiN_x$ 200 nm, OLED #1 / $SiN_x$ 400 nm and OLED #1 / $SiN_x$ 400 nm / metal film was 7, 12, 25, and 45 hours, respectively. In conclusion, it has been shown that the lifetime of OLEDs can be improved more than 6 times by $SiN_x$ film and a metal film encapsulation.

• Proceedings of the Materials Research Society of Korea Conference
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• 2008.11a
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• pp.32.1-32.1
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• 2008

• International Journal of Contents
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• v.2 no.3
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• pp.6-10
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• 2006

Small molecule OLED devices were fabricated and the electro-optical characteristics were analyzed. The luminance and color coordinate of the fabricated OLED device were $24,390cd/m^2$ and (x=0.15, y=0.22), respectively. Current efficiency of 6.8 cd/A and power efficiency of 2.4 lm/W were also obtained under DC operating condition. Transient light intensity was also measured by using Si photodiode.

• 한국정보디스플레이학회:학술대회논문집
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• 2003.07a
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• pp.920-923
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• 2003

We fabricated composite materials as a pellet structure with the various kinds of inorganic material powder. The composite materials were deposited onto the plastic film by the electron beam evaporation and water vapor transmission rates (WVTRs) were measured by the MOCON facility. As a result of WVTRs, the composite materials had lower WVTR value than any other inorganic materials. So, these films were proposed to protect the organic light emitting device (OLED) from moisture and oxygen. We can consider that the composite thin-film is one of the more suitable candidates for the thin-film passivation layer in the OLED. And, we are processing the XRD, XPS and EPMA to analyze the property of the composite material. We will also analyze properties of the current-voltage and luminescence for lifetime both the composite thin-film passivated OLED and non-passivated OLED.

• 한국정보디스플레이학회:학술대회논문집
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• 2003.07a
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• pp.4-6
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• 2003

We have developed the active matrix OLED displays with a high efficiency red emission material which uses an emitting assist (EA) dopant system. The EA dopant (rubrene) did not itself emit but assisted the energy transfer from the host ($Alq_s$) to the red emitting dopant(DCM2). A stable red emission (chromaticity coordinates: x=0.64, y=0.36) was obtained in this cell within the luminance range of 100 - 4000 $cd/m^2$ By using EA dopant system, we can realize the reduction of the power consumption of the OLED display..