• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.147.2-147.2
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• 2014

Organic Light Emitting Diode (OLED)에 사용되는 유기재료 N,N.-diphenyl-N,N.-bis(1-naphthyl)-1,1'-biphenyl-4,4"-diamine(NPB)의 상전이 특성을 여러 진공도에서 평가하였다. 압력, 온도제어가 가능한 진공시스템을 사용하여 여러 진공도에서 NPB의 상전이 온도를 측정하였고, 본 연구에 사용된 진공시스템의 신뢰성을 검증하기 위해 상압에서 측정한 NPB의 melting temperature를 Differential Scanning Calorimetry(DSC) data와 비교하였다. 또한 각 압력($10^{-7}{\sim}760Torr$)에서 측정한 상전이 온도를 바탕으로 최종 결과물인 NPB의 Phase diagram을 얻어냄으로써 일정 압력, 일정 온도에서의 NPB의 상거동을 예측할 수 있었다. 이러한 결과는 기존의 DSC열분석으로는 확인하기 어려웠던 진공에서의 유기재료의 상전이를 관측하였다는데 큰 의미가 있다. 향후, 이러한 방법을 활용한 진공에서의 유기재료의 상전이 특성 관측은 유기재료를 이용한 진공 증착공정방법의 최적화와, 다양한 유기재료의 열안정성 특성 파악에 도움이 될 것으로 기대가 된다.

• 한국전기전자재료학회논문지
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• 제21권2호
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• pp.173-177
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• 2008

We have developed the transparent passivation layer for top emission organic light emitting diodes using CsCl thin film by the thermal evaporation method. The CsCl film was deposited on the Ca/Ag semitransparent cathode. The optical transmittance of Ca/ Ag/CsCl triple layer is higher than that of Ca/Ag double layer in the visible range. The device with a structure of glass/Ni/2-TNATA/a-NPD/Alq3:C545T/BCP/Alq3/Ca/Ag/CsCl results in higher efficiency than the device without CsCl passivation layer. The device without CsCl thin film shows a current efficiency of 7 cd/A, whereas the device passivated with CsCl layer shows an efficiency of 10 cd/A. This increase of efficiency isresulted from the increased optical extraction by the CsCl passivation layer.

• 한국전기전자재료학회논문지
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• 제19권6호
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• pp.563-567
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• 2006

Indium tin oxide (ITO) used as an electrode in organic light emitting diodes (OLEDs) and organic thin film transistors (OTFTs) was modified by a self-assembled monolayer (SAM). For device fabrication, surface of the ITO was modified by immersion in a solution including various phosphonic acid at room temperature in order to increase work function of an electrode. The work function of ITO with SAM was measured by Kelvin probe. Work function increase of 0.88 eV was observed in ITO with various SAM. Therefore, ohmic contact is achieved in an interface between ITO and organic semiconductors (pentacene). We analyzed the origin of work function increase of ITO with SAM by X-ray photoelectron spectroscopy. We confirmed that increase of oxygen bonding energy attributed to increase the work function of ITO. These results suggested that ITO with the SAM gives a high possibility for high performance of OLEDS and OTFTs.

• 전자공학회논문지 IE
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• 제43권2호
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• pp.1-6
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• 2006

Two-wavelength에 의한 백색 유기발광소자를 청색계열의 발광재료 DPVBi와 오렌지계열의 발광재료 Rubrene 물질을 사용하여 제작하였다. 소자의 구조는 glass/ITO/TPD$(225{\AA})$/DPVBi/Rubrene/BCP$(210{\AA})/Alq_3(225{\AA})/Al(1000{\AA})$로 하였다. 청색 발광층인 DPVBi와 오렌지색 발광층인 Rubrene층의 두께비율를 변화시켜 가면서 백색광을 구현하였다. 청색발광재료 DPVBi층의 두께가 210${\AA}$ 이고 오렌지색 발광재료의 Rubrene 층의 두께가 180${\AA}$일 때 구동전압 15V에서 $1000cd/m^2$ 휘도와 (0.29, 0.33)의 CIE 색좌표값을 갖는 백색광을 얻었다.

• ETRI Journal
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• 제43권6호
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• pp.1093-1102
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• 2021

Microdisplays based on organic light-emitting diodes (OLEDs) have a small form factor, and this can be a great advantage when applied to augmented reality and virtual reality devices. In addition, a high-resolution microdisplay of 3000 ppi or more can be achieved when applying a white OLED structure and a color filter. However, low luminance is the weakness of an OLED-based microdisplay as compared with other microdisplay technologies. By applying a tandem structure consisting of two separate emission layers, the efficiency of the OLED device is increased, and higher luminance can be achieved. The efficiency and white spectrum of the OLED device are affected by the position of the emitting layer in the tandem structure and calculated via optical simulation. Each white OLED device with optimized efficiency is fabricated according to the position of the emitting layer, and red, green, and blue spectrum and efficiency are confirmed after passing through color filters. The optimized white OLED device with color filters reaches 97.8% of the National Television Standards Committee standard.

• Current Optics and Photonics
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• 제3권6호
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• pp.485-495
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• 2019

Photobiomodulation (PBM) using organic light emitting diodes (OLEDs) surface light sources have recently been claimed to be the next generation of PBM light sources. However, the differences between light emitting diodes (LEDs) and OLED mechanisms in vitro and in vivo have not been well studied. In vivo mouse models were used to investigate the effects of OLED irradiation on cellular function and cutaneous wound healing compared to LED irradiation. Mice in the LED- and OLED-irradiated groups were subjected to irradiation with 6 J/㎠ LED and OLED (630 nm), respectively, for 14 days after wounding, and some mice were sacrificed for the experiments on days 3, 7, 10, and 14. To evaluate wound healing, we performed hematoxylin-eosin and Masson's trichrome staining and quantified collagen density by computerized image analysis. The results showed that the size of the wound, collagen density, neo-epidermis thickness, number of new blood vessels, and number of fibroblasts and neutrophils was significantly influenced by LED and OLED irradiation. The tissue levels of interleukin (IL)-β, IL-6 and tumor necrosis factor (TNF)-α were investigated by immunohistochemical staining. LED and OLED irradiation resulted in a significant increase in the tissue IL-β and IL-6 levels at the early stage of wound healing (P < 0.01), and a decrease in the tissue TNF-α level at all stages of wound healing (P < 0.05), compared to the no-treatment group. The expression levels of the genes encoding vascular endothelial growth factor and transforming growth factor-beta 1 were significantly increased in LED and OLED-irradiated wound tissue at the early stage of wound healing (P < 0.01) compared to the no-treatment group. Thus, OLED as well as LED irradiation accelerated wound healing by modulating the synthesis of anti-inflammatory cytokines and the expression levels of genes encoding growth factors, promoting collagen regeneration and reducing scarring. In conclusion, this suggests the possibility of OLED as a new light source to overcome the limitations of existing PBMs.

• 대한전자공학회논문지SD
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• 제42권12호
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• pp.13-18
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• 2005

본 논문에서는 Poly-ethylene-terephthalate (PET) 기판 위에 Organic Thin Film Transistor (OTFT)와 Organic Light Emitting Diode (OLED)를 직렬 연결시킨 픽셀과 64 x 64 픽셀로 구성된 어레이를 제작하여 동작을 시연하였다. OTFT는 PET 기판과의 호환성을 고려하여 Poly 4-vinylphenol을 게이트 절연체로, 펜타센을 활성층으로 사용하여 제작되었다. 개별 소자 수준에서는 이동도가 $1.0\;cm^2/V{\cdot}sec$로 나타났으나, 어레이에서는 $0.1\~0.2\;cm^2/V{\cdot}sec$로 약 10배 정도 감소하였다. 어레이의 동작을 분석하였고 OTFT의 OLED에 대한 전류구동능력을 확인하였다.

• 한국산학기술학회논문지
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• 제11권3호
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• pp.827-834
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• 2010

발광층에 도펀트가 도핑된 다층 유기발광다이오드 소자 구조에서의 발광 메카니즘을 검증하기 위해 전기적인 특성요인들을 수치해석 하였다. 본 논문에 적용한 유기발광다이오드 소자는 ITO/NPB/$Alq_3$:C545T(%)/$Alq_3$/LiF/Al으로 이루어져 있으며 도펀트인 C545T의 도핑 농도를 변화시킨 4종류의 소자 구조에 대해 특성 변화를 검토하였다. 그 결과 도펀트의 도핑 농도 변화에 따라서 전압-전류 특성이 변화되어짐을 확인하였고, 이는 참고 문헌에 제시되어 있는 전압-전류밀도 실험 데이터와 매우 잘 일치되었다. 또한 도펀트를 도핑시킨 소자 구조들에서 전압-휘도 특성이 대폭 향상되어 발광효율이 3배정도 향상되었다. 이와 같은 guest-host system이 적용된 유기발광다이오드 소자의 동작 메카니즘을 분석하기 위하여 소자 내부에서의 전계분포, 전하분포, 재결합율 등의 전기적인 항목들에 대한 특성의 변화를 관찰하였다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 춘계학술대회 논문집
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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.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2004년도 Asia Display / IMID 04
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• pp.277-280
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• 2004

Thin-film photosensors on organic light emitting diode (OLED) glass substrates using active-matrix OLED TFT manufacturing processes have been constructed and optimized, and their performance has been characterized. Suitable control circuitry and applications are proposed. The photosensors may be integrated into OLED displays for detection of ambient illumination and for detection of OLED light emission, thereby enabling output, uniformity, and aging compensation.