• Title/Summary/Keyword: Hybrid white organic light-emitting diodes

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Highly efficient white organic light-emitting diodes using hybrid-spacer or/and codoped blue emitting layers

  • Seo, Ji-Hoon;Kim, Gu-Young;Hyung, Gun-Woo;Lee, Kum-Hee;Kim, You-Hyun;Kim, Woo-Young;Yoon, Seung-Soo;Kim, Young-Kwan
    • 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.

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The Spacer Thickness Effects on the Electroluminescent Characteristics of Hybrid White Organic Light-emitting Diodes

  • Seo, Ji-Hoon;Park, Jung-Sun;Seo, Bo-Min;Kim, Young-Kwan;Lee, Kum-Hee;Yoon, Seung-Soo
    • Transactions on Electrical and Electronic Materials
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    • v.10 no.6
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    • pp.208-211
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    • 2009
  • The authors have demonstrated the various characteristics of hybrid white organic light-emitting diodes (HWOLED) using fluorescent blue and phosphorescent red emitters. We also demonstrated that two devices showed different characteristics in accordance with thickness of the 4,4′-N,N′-dicarbazole-biphenyl (CBP) spacer (CS) inserted between the blue and the red emitting layer. It was found that the device with a CS thickness of 70 $\AA$ showed a current efficiency 2.5 times higher than that of the control device with a CS thickness of 30 $\AA$ by preventing the triplet Dexter energy transfer from the red to the blue emitting layer. The HWOLED with the CS thickness of 70 $\AA$ exhibited a maximum luminance of 24500 cd/$m^2$, a maximum current efficiency of 42.9 cd/A, a power efficiency of 37.5 lm/W, and Commission Internationale de I'Eclairage coordinates of (0.37, 0.42).

High Efficiency Hybrid White Organic Light-Emitting Diodes for Reduced Efficiency Roll-Off and Color Stability

  • Seo, Ji-Hoon;Park, Jung-Sun;Kim, Jun-Ho;Koo, Ja-Ryong;Seo, Bo-Min;Lee, Kum-Hee;Park, Jeong-Keun;Je, Jong-Tae;Yoon, Seung-Soo;Kim, Young-Kwan
    • 한국정보디스플레이학회:학술대회논문집
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    • 2009.10a
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    • pp.418-420
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    • 2009
  • The Authors have demonstrated high efficiency hybrid white organic light-emitting diodes (HWOLED) for reduced efficiency roll-off and color stability. It was shown that HWOLED fabricated in this study have the maximum luminance of 46 420 cd/$m^2$ at 8 V (turn-on voltage of 2.7 V), external quantum efficiency of 13.18%, power efficiency of 28.75 lm/W at 1 000 cd/$m^2$, and reduced efficiency roll-off of 2.7 times than control white device. The HWOLED also showed the stable color shift with $\Delta$Commission Internationale de I'Eclairage coordinates coordinates of ${\pm}$ (0.00, 0.00) from 100 to 10000 cd/$m^2$.

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Optical and Electrical Properties of Two-Wavelength White Tandem Organic Light-Emitting Diodes Using Red and Blue Materials (적색과 청색 물질을 사용한 2파장 방식 백색 적층 OLED의 광학 및 전기적 특성)

  • Park, Chan-Suk;Jua, Sung-Hoo
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.28 no.9
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    • pp.581-586
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    • 2015
  • We studied optical and electrical properties of two-wavelength white tandem organic light-emitting diodes using red and blue materials. White fluorescent OLEDs were fabricated using Alq3 : Rubrene (3 vol.% 5 nm) / SH-1 : BD-2 (3 vol.% 25 nm) as emitting layer (EML). White single fluorescent OLED showed maximum current efficiency of 9.7 cd/A, and tandem fluorescent OLED showed 18.2 cd/A. Commission Internationale de l'Eclairage (CIE) coordinates of single and tandem fluorescent OLEDs was (0.385, 0.435), (0.442, 0.473) at $1,000cd/m^2$, respectively. White hybrid OLEDs were fabricated using SH-1 : BD-2 (3 vol.% 10 nm) / CBP : $Ir(mphmq)_2(acac)$ (2 vol.% 20 nm) as EML. White single hybrid OLED showed maximum current efficiency of 7.8 cd/A, and tandem hybrid OLED showed 26.4 cd/A. Maximum current efficiency of tandem hybrid OLED was more twice as high as single OLED. CIE coordinates of single hybrid OLED was (0.315, 0.333), and tandem hybrid OLED was (0.448, 0.363) at $1,000cd/m^2$. CIE coordinates in white tandem OLEDs compared to those for single OLEDs observed red shift. This work reveals that stacked white OLED showed current efficiency improvement and red shifted emission than single OLED.

Highly efficient and transparent white OLED for lighting

  • Lee, Jeong-Ik;Lee, Jong-Hee;Lee, Joo-Won;Shin, Jae-Heon;Chu, Hye-Yong
    • 한국정보디스플레이학회:학술대회논문집
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    • 2009.10a
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    • pp.482-485
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    • 2009
  • We have fabricated transparent white organic light emitting diodes (WOLEDs) for lighting application. The structure property relationship of hybrid WOLEDs has been investigated and optimized devices showed high efficiency. Introduction of transparent cathode of LiF/Al/Ag into the hybrid WOLED led highly efficient WOLED with good transparency.

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Improvement of Color Purity Using Hole Blocking Layer in Hybrid White OLED (Hole Blocking Layer 사용에 따른 하이브리드 백색 OLED의 색순도 향상에 관한 연구)

  • Kim, Nam-Kyu;Shin, Hoon-Kyu;Kwon, Young-Soo
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.27 no.12
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    • pp.837-840
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    • 2014
  • Novel materials of $Zn(HPB)_2$ and Ir-complexes were respectively synthesized as blue or red emitting material. White Organic Light Emitting Diodes (OLED) were fabricated by using $Zn(HPB)_2$ for a blue emitting layer, Ir-complexes for a red emitting layer and $Alq_3$ for a green emitting layer. White OLED was fabricated by using double emitting layers of $Zn(HPB)_2$ and $Alq_3:Ir$-complexes, and hole blocking layer of BCP. We also varied the thickness of BCP. When the thickness of BCP layer was 5 nm, white emission was achieved. We obtained a maximum luminance of $3,500cd/m^2$. The CIE coordinates was (0.375, 0.331). From this study, we could propose that the hybrid structure is efficient in lighting application of white OLED by improvement of color purity.

Improvement of Efficiency Varying Ratio in Hybrid White OLED (도핑 비율에 따른 하이브리드 백색 OLED의 효율 향상에 관한 연구)

  • Kim, Nam-Kyu;Shin, Hoon-Kyu;Kwon, Young-Soo
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.27 no.9
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    • pp.571-575
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    • 2014
  • We synthesized new materials of $Zn(HPB)_2$ and Ir-complexes as blue or red emitting material. We fabricated white Organic Light Emitting Diodes (OLED) by using $Zn(HPB)_2$ for the blue emitting layer, Ir-complexes for the red emitting layer and $Alq_3$ for the green emitting layer. We fabricated white OLED by using double emitting layers of $Zn(HPB)_2$:Ir-complexes and $Alq_3$. The doping rate of Ir-complexes was varied, such as 0.2%, 0.4%, 0.6%, and 0.8%, respectively. When the doping rate of $Zn(HPB)_2$:Ir-complexes was 0.6%, white emission was achieved. The Commission Internationale de l'Eclairage (CIE) coordinates of the white emission was (0.322, 0.312).

Synthesis and Characterization of Red Organic Fluorescent of Perylene Bisimide Derivatives (Perylene Bisimide 유도체의 적색 유기 형광체 합성 및 특성 연구)

  • Lee, Seung Min;Jeong, Yeon Tae
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.30 no.9
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    • pp.577-582
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    • 2017
  • The white light of a hybrid LED is obtained by using red and green organic fluorescent layers made of polymethylmethacrylate (PMMA) films, which function as color down-conversion layers of blue light-emitting diodes. In this research, we studied the fluorescence properties of a red organic fluorophore, employing perylene bisimide derivatives applicable to hybrid LEDs. The solubility, thermal stability, and luminous efficiency are important characteristics of organic fluorophores for use in hybrid LEDs. The perylene fluorescent compounds (1A and 1B) were prepared by the reaction of 4-bromophenol and 4-iodophenol with N,N'-bis(4-bromo-2,6-diisopropylphenyl)-1, 6,7,12-tetrachloroperylene-3,4,9,10-tetracarboxyl diimide (1) in the presence of dimethyl formaldehyde (DMF) at $70^{\circ}C$. The synthesized derivatives were characterized by using $^1H-NMR$, FT-IR, UV/Vis absorption and PL spectra, and TGA analysis. Compounds 1A and 1B showed absorption and emission at 570 nm and 604 nm in the UV/Vis spectrum. We also documented favorable solubility and thermal stability characteristics of the perylene fluorophores in our work. Perylene fluorophore 1, with the 4-bromophenol substituent 1A, exhibited particularly good thermal stability and solubility in organic solvents.

A Hybrid Spacer Effect on White Organic Light-Emitting Diodes with Phosphorescent Emitters (인광 발광 물질을 이용한 백색 유기 발광 다이오드에서의 혼합된 스페이서의 영향에 관한 연구)

  • Seo, Ji-Hoon;Park, Jung-Sun;Hyung, Gun-Woo;Seo, Ji-Hyun;Lee, Kum-Hee;Yoon, Seung-Soo;Kim, Young-Kwan
    • Journal of the Korean Applied Science and Technology
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    • v.26 no.1
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    • pp.24-28
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    • 2009
  • 본 논문에서는 청색 인광 발광 물질인 bis(3,5-Difluoro-2-(2-pyridyl)phenyl-(2-carboxypyridyl) iridium (III) (Flrpic)과 녹색 인광 발광 물질인 fac-tris(2-phenypyridine) irdium(III) ($Ir(ppy)_3$)와 적색 인광 발광 물질인 his(5-benzoyl-2-phenylpyridinato-C,N)iridium(III) (acetylacetonate) ($(Bzppy)_{2}Ir(acac)$)를 각각 적층하여 백색 유기 발광 다이오드를 제작하였고, 각각의 발광층 사이에 혼합된 스페이서인 4,4'-N,N'-dicarbazole-biphenyl (CBP):4,7-diphenyl-1,10-phenanthroline (BPhen)을 적층하여 그 때의 영향에 대하여 연구하였다. 최적화된 구조에서의 전력 효율은 $0.014\;mA/cm^2$에서의 19.7 lm/w를 나타내었으며, $0.127\;mA/cm^2$에서의 11.5%의 외부 양자 효율을 나타내었고, 8 V에서 Commission Internationale do I'Eclairage ($CIE_{x,y}$) coordinates (x=0.36, y=0.44)의 색좌표를 나타내었다.