• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.2018-2019
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• 2007

Organic light emitting diodes (OLEDs) show a lot of advantages for display purposes. Because OLEDs provide white light emission with a high efficiency and stability, it is desirable to apply OLEDs as an illumination light source and back light in LCD displays. We synthesized new emissive materials, namely $Zn(HPB)_2$ and Zn(HPB)q, which have a low molecular compound and thermal stability. We studied white OLEDs using $Zn(HPB)_2$ and Zn(HPB)q. The fundamental structures of the white OLEDs were ITO / NPB (40 nm) / $Zn(HPB)_2$ (40 nm) / Zn(HPB)q (20 nm) / LiAl (120nm). As a result, we obtained a maximum luminance of $15325cd/m^2$ at a current density of $997\;mA/cm^2$. The CIE (Commission International de l'Eclairage) coordinates are (0.28, 0.35) at an applied voltage of 9.75 V.

• Journal of Information Display
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• v.12 no.1
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• pp.51-55
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• 2011

Efficient two-color-mixed white organic light-emitting diodes are presented herein by employing a sky-blue phosphorescent dopant of iridium(III)bis[4,6-(difluorophenyl)-pyridinato-N,$C^{2'}$]picolinate (FIrpic) and an orange phosphorescent dopant of bis(2-phenylquinoline)(acetylacetonate)iridium(III) ($Ir(phq)_2$acac) on the emissive layer. Very stable color variation under ${\Delta}$0.02 until a 5000 cd/$m^2$ brightness value was realized by efficient carrier control in a multi-stacked emitting layer of blue/red/blue colors. Maximum current and power efficiencies of 23.8 cd/A and 22.9 lm/W in the forward direction were obtained. With balanced emission from the two emitters, the white-light emission of high correlated color temperature of 7308K and the Commission Internationale de I'Eclairage coordinates of (0.30, 0.33) were achieved.

• ETRI Journal
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• v.36 no.5
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• pp.847-855
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• 2014

We developed a highly refractive index planarization layer showing a very smooth surface for organic light-emitting diode (OLED) light extraction, and we successfully prepared a highly efficient white OLED device with an embossed nano-structure and highly refractive index planarization layers. White OLEDs act as an internal out-coupling layer. We used a spin-coating method and two types of $TiO_2$ solutions for a planarization of the embossed nano-structure on a glass substrate. The first $TiO_2$ solution was $TiO_2$ sol, which consists of $TiO_2$ colloidal particles in an acidic aqueous solution and several organic additives. The second solution was an organic and inorganic hybrid solution of $TiO_2$. The surface roughness ($R_a$) and refractive index of the $TiO_2$ planarization films on a flat glass were 0.4 nm and 2.0 at 550 nm, respectively. The J-V characteristics of the OLED including the embossed nano-structure and the $TiO_2$ planarization film were almost the same as those of an OLED with a flat glass, and the luminous efficacy of the aforementioned OLED was enhanced by 34% compared to that of an OLED with a flat glass.

• Korean Journal of Materials Research
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• v.16 no.4
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• pp.231-234
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• 2006

To obtain balanced white-emission and high efficiency of the organic light-emitting diodes (OLEDs), a deep blue emitter made of N,N'-diphenyl-N,N'-bis(1-naphthyl)- (1,1'-biphenyl)-4,4'-diamine (NPB) emitter and a new red emitter made of the Bis(2,4 -dimethyl-8-quinolinolato)(triphenylsilanolato)aluminum(III) (24MeSAlq) doped with red fluorescent 4-(dicyanomethylene)-2-tert-butyl-6-(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H -pyran (DCJTB) were used and the device was tuned by varying the thickness of the DCJTB-doped 24MeSAlq and $Alq_3$. For the white OLED with 10 nm thickness DCJTB (0.5%) doped 24MeSAlq and 45 nm thick $Alq_3$, the maximum luminance of about 29,700 $Cd/m^2$ could be obtained at 14.8 V. Also, Commission Internationale d'Eclairage (CIE) chromaticity coordinates of (0.32, 0.28) at about 100 $Cd/m^2$, which is very close to white light equi-energy point (0.33, 0.33), could be obtained.

• 한국정보디스플레이학회:학술대회논문집
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• 2008.10a
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• pp.1120-1123
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• 2008

Efficient, color stable multi-EML WOLED have been fabricated using newly synthesized yellowish green dopant Ir(chpy)3 or Ir(mchpy)3. The devices have high external quantum efficiency of 11.7%, color rendering index of 87, variation of CIE coordinate of (0.02, 0.01) between 10 to 5000 cd/m2, and low roll-off in efficiency with increasing brightness.

• 한국정보디스플레이학회:학술대회논문집
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• 2009.10a
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• pp.820-822
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• 2009

Tandem white organic light emitting diodes (WOLEDs) are fabricated by using a transparent interconnecting layer of Al:LiF composite/molybdenum oxides ($MoO_3$). We demonstrate two types of tandem WOLEDs consisting of two color emissions (red and blue emission) and three color emissions (red, green and blue emission). Tandem WOLED consisting of three color emission shows higher external quantum efficiency and current efficiency.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.24 no.6
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• pp.486-490
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• 2011

To investigate the effect of two-emission-layer structure on the emission characteristics of the phosphorescent white organic light-emitting diodes (PHWOLEDs), the PHWOLEDs with two different emission layers, blue EML(29 nm, FIrpic-doped mCP) and red EML(1 nm, Ir(pq)$_2$acac-doped CBP)), following host-guest system were fabricated. The bi-layered blue EML was composed of mCP:FIrpic (20 nm, 7 vol.%) and mCP:FIrpic (9 nm, 7, 10, 15, 20, and 25 vol.%, respectively). When the concentration of FIrpic was increased from 7 to 15 vol.%, light emission luminance, current efficiency, and external quantum efficiency were increased. On the contrary, when the concentration of FIrpic was increased to more than 20 vol.%, light emission luminance, current efficiency, and external quantum efficiency were decreased. The PHWOLEDs with the bi-layered blue EML structure of mCP:FIrpic (20 nm, 7 vol.%) and mCP:FIrpic (9 nm, 15 vol.%) showed current efficiency of 29.7 cd/A and external quantum efficiency (EQE) of 16.6% at 1,000 $cd/cm^2$.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.26 no.1
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• pp.15-21
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• 2012

In this study, the characteristics of the 2-wavelength white organic light-emitting diod (WOLED) with two colors of yellow and blue were compared and analyzed with 3-wavelength WOLED with three colors of red, green, and blue. The results indicated that the power efficiency of the 2-wavelength WOLED was 1.6 times higher than 3-wavelength WOLED. In addition, the colot coordinate of the 2-wavelenth WOLED which was (0.34, 0.39) was found closer to the optimal color coordinate for the white-lighting application when compared with that of the 3-wavelength WOLED.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.8 no.2
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• pp.25-31
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• 2009

The image processing methods are widely used in many industrial fields to detect defections in inspection devices. In this study an image processing method was conducted for the detection of abnormal pixels in a OLED(Organic Light Emitting Diode) type panel which is used for small size displays. The display quality of an OLED device is dependent on the pixel formation quality. So, among the so many pixels, to find out the faulty pixels is very important task in manufacturing processing or inspection division. We used a line scanning type BW(Black & White) camera which has very high resolution characteristics to acquire an image of display pixel patterns. And the various faulty cases in pixel abnormal patterns are considered to detect abnormal pixels. From the results of the research, the normal BW pixel image could be restored to its original color pixel.

• 한국정보디스플레이학회:학술대회논문집
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• 2007.08b
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• pp.1429-1432
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• 2007

We fabricated white organic light emitting diodes(WOLED) having two complementary and three primary colors with emission layers of DPVBi / MADN : DCM2-0.5% and DPVBi / $Alq_3$ / MADN : DCM2-1.5%, respectively. WOLED using three primary colors shows broad electroluminescence including green emission peak at 510nm while optical properties of the two complementary WOLED was higher current efficiency of 6.2 cd/A than 4.9 cd/A of three primary color WOLED. The maximum luminescence of WOLED with two complimentary color was $15200cd/m^2$ along with luminous efficiency 6.2cd/A, as achieving stable white color coordinates for both of WOLEDs at (0.33 , 0.33) almost.