• Transactions on Electrical and Electronic Materials
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• v.12 no.2
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• pp.80-83
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• 2011

We have fabricated phosphorescent white organic light-emitting devices (WOLEDs) with a spin-coated poly(Nvinylcarbazole) [PVK] host layer. Iridium(III) bis[(4,6-difluorophenyl)-pyridinato-N,$C^{2'}$]picolinate (FIrpic), tris(2-phenylpyridine)iridium(III) [$Ir(ppy)_3$], and tris(2-phenyl-1-quinoline)iridium(III) [$Ir(phq)_3$], were used as the blue, green, and red guest materials, respectively. The PVK was mixed with FIrpic, $Ir(ppy)_3$, and $Ir(phq)_3$ molecules in a chlorobenzene solution and spin-coated in order to prepare the emission layer; 3-(4-biphenylyl)-4-phenyl-5-(4-tertbutylphenyl)-1,2,4-triazole (TAZ) was used as an electron transport material. The resultant device structure was ITO/PVK:FIrpic:$Ir(ppy)_3:Ir(phq)_3$/TAZ/LiF/Al. The electroluminescence, efficiency, and electrical conduction characteristics of the WOLEDs based on the doped PVK host layer were investigated. The maximum current efficiency of the three wavelength WOLED with the doped PVK host was 19.2 cd/A.

• 한국정보디스플레이학회:학술대회논문집
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• 2007.08b
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• pp.1399-1402
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• 2007

We have demonstrated efficient white WOLEDs by using three emissive materials for primary colors (red, green, and blue). The characteristics of WOLEDs showed the maximum luminance of $37600\;cd/m^2$ at 13V, the maximum luminous efficiency of 20.6 cd/A, and the $CIE_{xy}$ coordinates of (x = 0.33, y = 0.33) at 10V.

• 한국정보디스플레이학회:학술대회논문집
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• 2008.10a
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• pp.1215-1218
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• 2008

We investigate the effect of a light emitting layer (EML) sequence and an interlayer on the performance of the phosphorescent-fluorescent mixed white organic light emitting diodes. Two types of phosphorescent-fluorescent mixed system were evaluated. The proper position of each primary color EML was crucial to obtain best performance in each system whereas the effect of an interlayer was found to be different in both systems.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07a
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• pp.192-195
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• 2004

적록청(Red, Green, Blue : RGB)의 세 기본 염료(primary dyes)를 사용하여 백색 유기전계발광소자(White Organic Light Emitting Devices : WOLEDs)을 유기물 분자선 증착(Organic Molecular Beam Deposition)방법에 의해서 제작하였다. 소자의 구조는 $ITO/{\alpha}-NPD(40nm)/DPVBi(6nm)/Alq_3(12nm)/Alq_3:DCJTB(7nm,3%)\;or\;DPVBi:DCJTB(7nm,3%)/Alq_3(35nm)/MgAg(150nm)$으로, red 발광층의 host 물질을 $Alq_3$ 또는 DPVBi의 두 종류를 사용하여 소자를 제작하였다. 이들 소자들은 전류밀도가 증가함에 따라 스펙트럼 곡선의 변화가 거의 보이지 않았으며, 색좌표는 전류밀도 $20mA/cm^2$에서 (0.34,0.34)이고 $100mA/cm^2$에서(0.32,0.33)으로 비교적 안정적이였다. $Alq_3$을 red 발광층의 host로 사용한 소자는 $10mA/cm^2({\sim}6V)$에서 luminance yield가 1.87cd/A 또는 $100cd/m^2({\sim}5.5V)$에서는 발광효율 1.21m/w으로, DPVBi을 red 발광층의 host로 사용한 소자보다 약 20%의 효율향상을 보였다. 그러나 전류밀도 $30mA/cm^2$ 이상에서는 발광효율이 반전되어 나타났다. 이런 현상은 DPVBi을 red 발광층의 host로 사용한 소자가 $Alq_3$을 red 발광층의 host로 사용한 소자보다 발광 소광 현상이 적게 일어난 것에 기인하였다고 생각된다. 두 소자 모두 $40mA/cm^2$ 에서 이상적인 화이트 발란스와 같은(0.33,0.33)의 색좌표를 보였다.

• 한국정보디스플레이학회:학술대회논문집
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• 2008.10a
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• pp.1219-1221
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• 2008

The Authors have demonstrated highly efficient white organic light-emitting diodes using hybrid-spacer which was inserted between each emitting layer or/and codoped blue emitting layers with the different functional material. The characteristics of WOLEDs showed the maximum external quantum efficiency of 13.8%, power efficiency of 33.66 lm/W, and Commission Internationale de I'Eclairage coordinates of (x=0.36, y=0.37), respectively.

• 한국정보디스플레이학회:학술대회논문집
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• 2008.10a
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• pp.1116-1119
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• 2008

We developed phosphorescent white OLEDs with high efficiency and color stability. By engineering device architecture in which confined excitons within the emissive layer by using adequate interlayer and balanced recombination of charge carriers by using stepwise hole transporting layer system, these WOLEDs showed power efficacy of 43.6 lm/W with CRI = 62 and 36 lm/W with CRI = 72 at $100\;cd/m^2$ without outcoupling enhancements.

• 한국정보디스플레이학회:학술대회논문집
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• 2006.08a
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• pp.1002-1005
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• 2006

In this study, we fabricated white organic light emitting devices (WOLEDs) to use single emission layer, DPVBi with partially doped Rubrene. To realize white color, rubrene with 3.6% was partially doped with the gap from interface between DPVBi and hole transport layer NPD in a definite DPVBi layer. As the gap was increased, the intensity of orange peak grows less and less. The WOLED with gap of $5\;{\AA}$ has the best color stability and its color coordination is (0.345, 0.321) at 6V.

• Journal of the Korean Applied Science and Technology
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• v.25 no.1
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• pp.91-106
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• 2008

Development of white light emitting materials has been an interesting area for scientists and scientists have developed many organic, polymer and inorganic materials for white electroluminescent devices. Among them, single component small molecules gave best results in terms of efficiency, simplicity of device fabrication, and CIE values. Therefore, this review covers detailed discussion about syntheses of small compounds used in white organic light emitting devices until 2007.

• 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.

• Journal of Information Display
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• v.9 no.2
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• pp.18-21
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• 2008

We report on white organic light-emitting diodes (WOLEDs) based on single white dopants, $Ir(pq)_2$($F_2$-ppy) and $Ir(F_2-ppy)_2$(pq), where $F_2$-ppy and pq are 2-(2,4-difluorophenyl) pyridine and 2-phenylquinoline, respectively. The similar phosphorescent lifetime of two ligands lead to luminescence emission in two ligands simultaneously. However, the emission color of the devices was reddish, because the energy was not transferred efficiently from the 4,4,N,N'-dicarbazolebiphenyl (CBP) to the $F_2$-ppy ligand, due to the small band gap of the CBP. Accordingly, we used 1,4-phenylenesis(triphenylsilane) (UGH2) with a large band gap, instead of CBP as the host material. As a result, it was possible to adjust the emission color by the host material. The luminous efficiency of the device with $Ir(F_2-ppy)_2$(pq) doped in UGH2 was about 11 cd/A at 0.06 cd/$m^2$.