• 한국전기전자재료학회논문지
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• 제25권11호
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• pp.910-915
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• 2012

We studied the emission characteristics of white phosphorescent organic light-emitting diodes (PHOLEDs), which were fabricated using a two-wavelength method. The best blue emitting OLED and red emitting OLED characteristics were obtained at a concentration of 12 vol.% FIrpic and 1 vol.% $Bt_2Ir$(acac) in UGH3, respectively. And the optimum thickness of the total emitting layer was 25 nm. To optimize emission characteristics of white PHOLEDs, white PHOLEDs with red/blue/red, blue/red, red/blue and co-doping emitting layer structures were fabricated using a host-dopant system. In case of white PHOLEDs with co-doping structure, the best efficiency was obtained at a structure UGH3: 12 vol. % FIrpic: 1 vol.% $Bt_2Ir$(acac) (25 nm). The maximum brightness, current efficiency, power efficiency, external quantum efficiency, and CIE (x, y) coordinate were 13,430 $cd/m^2$, 40.5 cd/A, 25.3 lm/W, 17 % and (0.49, 0.47) at 1,000 $cd/m^2$, respectively.

• 한국표면공학회지
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• 제46권2호
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• pp.93-97
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• 2013

We studied the emission characteristics of white phosphorescent organic light-emitting diodes (PHOLEDs), which were fabricated using a two-wavelength method. To optimize emission characteristics of white PHOLEDs, white PHOLEDs with co-doping and blue/co-doping emitting layer (EML) structures were fabricated using a host-dopant system. The total thickness of light-emitting layer was 25 nm and the dopant of blue and red was FIrpic and $Bt_2Ir(acac)$ in UGH3, respectively. In case of co-doping structure, applying micro lens array film showed efficiency improvement from the current efficiency 78.5 cd/A and power efficiency 40.4 lm/W to the current efficiency 131.1 cd/A and power efficiency 65 lm/W and blue / co-doping structure showed efficiency improvement from the current efficiency 43.8 cd/A and power efficiency 22 lm/W to the current efficiency 69 cd/A and power efficiency 32 lm/W.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2009년도 9th International Meeting on Information Display
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• pp.415-417
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• 2009

Color stable and efficient two wavelength white organic light emitting diodes (OLEDs) were fabricated using a iridium(III)[bis(4,6-difluorophenyl)-pyridinato-N,$C^2$'] picolinate (FIrpic) as a blue phosphorescent emitter and a bis(1-phenylisoquinolinato-$C^2$,N)iridium (acetylacetonate) ((piq)$_2$Ir(acac)) as a red phosphorescent emitter. The emitting layers consist of two blue emitting layers and one red emitting layer which is between the two blue layers. The device reaches the peak efficiencies of 7.84 % and 10.3 cd/A at 0.6 mA/$cm^2$. Furthermore, there was little change of EL spectra according to current density change in the device.

• 한국전기전자재료학회논문지
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• 제22권10호
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• pp.850-853
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• 2009

We have optimized the device structure by using the dielectric layer such as anti-reflection thin film to improve the emitting efficiency of white organic light emitting device (WOLED). Basically, dielectric layer with anti-reflection characteristics can enhance the emitting efficiency of WOLED by compensating the refractive index of organic layer, ITO, and Glass. Here, WOLED was designed and optimized by Macleod simulator. The refractive index of 1.74 was calculated for Dielectric layer and was selected as $TiO_2$. The optimal thicknesses of $TiO_2$ and ITO were 119.3 and 166.6 nm, respectively, at the wavelength of 600 nm. The transmittance of ITO was measured with the thickness variation of dielectric layer and ITO in Organic layer/ITO/Dielectric layer structure. The transmittance of ITO was 95.17% and thicknesses of $TiO_2$ and ITO were 119.3 and 166.6 nm, respectively. This result, calculated and measured values were coincided.

• 한국재료학회지
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• 제15권8호
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• pp.543-547
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• 2005

Organic electroluminescence devices were made from 1,4-bis-(9-anthrylvinyl)benzene (AVB) and 1,4-bis-(9-aminoanthryl)benzene (AAB) anthracene derivatives. Device structure was ITO/AVB/PANI(EB)/Al (multi-layer device) and ITO/AAB:DCM/Al(single-layer device). In these devices, AVB, polyaniline(emeraldine base) (PANI(EB)) and AAB were used as the emitting material. 4-(dicyanomethylene)-2-methyl-6-p-(dimethylamino)styryl-4H -pyran(DCM) was used as red fluorescent dopant. We studied change of fluorescence wavelength with concentration of DCM doped in AAB. The ionization potential (IP) and optical band gap (Eg) were measured by cyclic voltammetry and UV-visible spectrum. We compared with difference of emitting wavelength between photoluminescence and electroluminescence spectrum. In case of the multi-layer device, PANI and AVB EL spectra have similar wave pattern to each PL spectrum and when PAM and AVB were used at the same time, and multi-layer device showed that a balanced recombination and radiation kom PANI and AVB. In case of the single-layer device, with the increase of DCM concentration, the blue emission decreases and red emission increases. This indicates that DCM was excited by the energy transfer from AAB to DCM or the direct recombination at the dopant sites due to carrier trapping, or both. The device with $1.0wt\%$ DCM concentration gave white light.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2004년도 학술대회지
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• pp.675-679
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• 2004

The existing conjugated blue emitting material polymer which has been used for the two-wavelength method white-emission has good stability and low operating voltage as merits, but the imbalanced carrier transport has been indicated as problem area. We have introduced a novel blue emitting material having perylene moiety unit with hole transporting ability and blue emitting property and triazine moiety unit with electron transporting ability into the same host chain. We have synthesized N-[p-(perylen-3-y1)pheny1]methacry1 amide (PPMA) monomer and [N-(2,4-dipheny1-1,3,5-triazine)pheny1 methacry1 amide] (DTPM) monomer having blue light-emitting unit and electron transport unit, respectively by three steps. A novel non-conjugated blue emitting material Poly[N -[p­(perylene-3-y1) pheny1] methacry1 amide-co-N-[P-(4,6-dipheny1-1,3,5-triazine-2-y1]pheny1]methacry1 amide] (PPPMA-co-DTPM) copolymer having electron transporting unit was synthesized by the solution polymerization of PPMA and DTPM monomers with an AIBN initiator and showed high yield of $75{\%}$. It was very soluble in common organic solvents, and the fabrication of the thin film using a spin coating method was very simple. The PPPMA exhibited a good thermal stability.