적색과 청색 물질을 사용한 2파장 방식 백색 적층 OLED의 광학 및 전기적 특성

박찬석,주성후,Park, Chan-Suk,Jua, Sung-Hoo 한국전기전자재료학회 2015 전기전자재료학회논문지 Vol.28 No.9

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.

청색과 적색 인광 물질을 사용한 백색 적층 OLED의 발광 특성

박찬석(Chan-Suk Park),주성후(Sung-Hoo Ju) 한국표면공학회 2016 한국표면공학회지 Vol.49 No.2

We studied white tandem organic light-emitting diodes using blue and red phosphorescent materials. Optimized white single phosphorescent OLED was fabricated using CBP : FIrpic (12 vol.%, 9 nm) / CBP : Ir(mphmq)₂acac : Ir(ppy)₃ (1 vol.%, 1 vol.%, 1 nm) as emitting layer (EML). The single phosphorescent OLED showed maximum current efficiency of 22.5 cd/A, white emission with a Commission Internationale de l"Eclairage (CIE) coordinates of (0.342, 0.37) at 1,000 cd/㎡, and variation of CIE coordinates with (0.339 ± 0.008, 0.371 ± 0.001) from 500 to 3,000 cd/㎡. Optimized white tandem phosphorescent OLED was fabricated using CBP : FIrpic (12 vol.%, 7 nm) / CBP : Ir(mphmq)₂acac : Ir(ppy)₃ (1 vol.%, 1 vol.%, 3 nm) as EML. The tandem phosphorescent OLED showed maximum current efficiency of 49.2 cd/A, white emission with a CIE coordinates of (0.376, 0.366) at 1,000 cd/㎡, variation of CIE coordinates with (0.375 ± 0.004, 0.367 ± 0.002) from 500 to 3,000 cd/㎡. Maximum current efficiency of tandem phosphorescent OLED was more twice as high as single phosphorescent OLED. Our results suggest that tandem phosphorescent OLED was possible to control CIE coordinates and produce excellent color stability.

Imprinted Microlens Array Films for Efficient Down-Conversion White Organic Light-Emitting Diodes

홍주희,한주원,김용현 한국공업화학회 2018 한국공업화학회 연구논문 초록집 Vol.2018 No.0

White organic light-emitting diodes (OLEDs) have attracted considerable attention due to their important applications in flat panel displays, general lighting. The biggest challenge of conventional OLEDs is the limited light outcoupling efficiency about 20 % while the internal quantum efficiency of OLEDs approaches almost 100 %. In this work, we develop a high performance down-conversion microlens array (DC-MLA) films for white OLEDs. The DC-MLA films are fabricated by a soft imprinting method with breath figure patterns, which are low-cost, simple and quick solution process. Blue OLEDs employing the DC-MLA films exhibit highly enhanced light outcoupling efficiency and high quality of white light. The DC-MLA films improve the external quantum efficiency (EQE) of white OLEDs by a factor of 1.45. In addition, high quality white light with a color rendering index of 84.3 is achieved for the white OLEDs with DC-MLA films.

청색 형광과 적색 인광 물질을 사용한 백색 OLED의 발광 특성

박찬석,주성후,Park, Chan-Suk,Ju, Sung-Hoo 한국전기전자재료학회 2015 전기전자재료학회논문지 Vol.28 No.11

We studied white organic light-emitting diodes using blue fluorescent and red phosphorescent materials. White single OLEDs were fabricated using SH-1 : BD-2 (3 vol.%) and CBP : $Ir(mphmq)_2(acac)$ (2 vol.%) as emitting layer (EML). The white single OLED using SH-1 : BD-2 (3 vol.% 8 nm) / CBP : $Ir(mphmq)_2(acac)$ (2 vol.% 22 nm) as emitting layer showed maximum current efficiency of 8.8 cd/A, Commission Internationale de l'Eclairage (CIE) coordinates of (0.403, 0.351) at $1,000cd/m^2$, and variation of CIE coordinates with ($0.402{\pm}0.012$, $0.35{\pm}0.002$) from 500 to $3,000cd/m^2$. The white tandem OLED using SH-1 : BD-2 (3 vol.% 12 nm) / CBP : $Ir(mphmq)_2(acac)$ (2 vol.% 18 nm) showed maximum efficiency of 19.6 cd/A, CIE coordinates of (0.354, 0.365) at $1,000cd/m^2$, and variation of CIE coordinates with ($0.356{\pm}0.016$, $0.364{\pm}0.002$) from 500 to $3,000cd/m^2$. Maximum current efficiency of the white tandem OLED was more twice as high as the single OLED. Our findings suggest that tandem OLED was possible to produce improved efficiency and excellent color stability.

Hole Blocking Layer 사용에 따른 하이브리드 백색 OLED의 색순도 향상에 관한 연구

김남규,신훈규,권영수,Kim, Nam-Kyu,Shin, Hoon-Kyu,Kwon, Young-Soo 한국전기전자재료학회 2014 전기전자재료학회논문지 Vol.27 No.12

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.

Color temperature tuning of white organic light-emitting diodes via spatial control of micro-cavity effects based on thin metal strips

Lee, Jonghee,Koh, Tae-Wook,Cho, Hyunsu,Hofmann, Simone,Reineke, Sebastian,Lee, Jae-Hyun,Lee, Jeong-Ik,Yoo, Seunghyup,Leo, Karl,Gather, Malte C. Elsevier 2015 Organic Electronics Vol.26 No.-

<P><B>Abstract</B></P> <P>White organic light-emitting diodes (WOLEDs) are one of the most promising technologies to realize future solid-state lighting with high power efficiency, broad and adjustable spectral coverage, and area emission for more effective and natural illumination. In this work, we report a new method of tuning the correlated color temperature (CCT) of WOLEDs via spatially controlling the degree of the micro-cavity effect in an OLED. Varying the width of thin Ag strips deposited on top of a transparent electrode leads to changes in both intensity and phase of reflection at the anode, hence significantly altering emission spectra of proposed WOLEDs. CCT of the implemented WOLEDs span a wide range, from 3000K to 8000K, demonstrating that our proposed approach helps to meet the need for lighting with various CCTs.</P> <P><B>Highlights</B></P> <P> <UL> <LI> We report a correlated color temperature (CCT) tunable white OLEDs. </LI> <LI> Micro-cavity (MC) effect in an OLED was controlled with a striped thin metal layer. </LI> <LI> MC effect alters emission spectra and intensity of white OLEDs. </LI> <LI> CCT of the implemented white OLEDs span a wide range, from 3000K to 8000K. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>White organic light-emitting diodes (WOLEDs) are one of the most promising technologies to realize future solid-state lighting with high power efficiency, broad and adjustable spectral coverage, and area emission for more effective and natural illumination. In this work, we report a new method of tuning the correlated color temperature (CCT) of WOLEDs via spatially controlling the degree of the micro-cavity effect in an OLED. Varying the width of thin Ag strips deposited on top of a transparent electrode leads to changes in both intensity and phase of reflection at the anode, hence significantly altering emission spectra of proposed WOLEDs. CCT of the implemented WOLEDs span a wide range, from 3000K to 8000K, demonstrating that our proposed approach helps to meet the need for lighting with various CCTs.</P> <P>[DISPLAY OMISSION]</P>

Design of white tandem organic light‐emitting diodes for full‐color microdisplay with high current efficiency and high color gamut

조현수,주철웅,최수경,강찬모,김기헌,신진욱,권병화,이현구,변춘원,조남성 한국전자통신연구원 2021 ETRI Journal Vol.43 No.6

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.

발광층 구조에 따른 백색 인광 OLED의 발광 특성

서정현,백경갑,주성후,Seo, Jung-Hyun,Paek, Kyeong-Kap,Ju, Sung-Hoo 한국전기전자재료학회 2012 전기전자재료학회논문지 Vol.25 No.6

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 red/blue, blue/red and red/blue/red emitting layer (EML) structures were fabricated using a host-dopant system. In case of white PHOLEDs with red/blue structure, the best efficiency was obtained at a structure of red (15 nm)/blue (15 nm). But the emission color was blue-shifted white. In case of white PHOLEDs with blue/red structure, the better color purity and efficiency were observed at a blue (29 nm)/red (1 nm) structure. For additional improvement of color purity in white PHOLEDs with blue (29 nm)/red (1 nm) EMLs, we fabricated white PHOLEDs with red (1 nm)/blue (28 nm)/red (1 nm) structure. The current efficiency, external quantum efficiency, and CIE (x, y) coordinate were 27.2 cd/A, 15.1%, and (0.382, 0.369) at 1,000 $cd/m^2$, respectively.

Binaphthyl group 기반의 물질을 이용한 효율적인 White OLED 소자에 대한 연구

여현기 한국유화학회 2012 한국응용과학기술학회지 Vol.29 No.3

본 연구에서 7,7'-(2,2'dimethoxy-1,1'-binaphthyl-3,3'-diyl) bis(4-(thiophen-2-yl) benzo[e] [1,2,5] thiadiazole (TBT) 라는 binaphthyl기를 기반으로 가지는 녹색 도판트 물질을 합성하였다. 추가적으로 인광 발광 물질인 iridium(III)bis[(4,6-di-fluoropheny)-pyridinato -N,C2]picolinate (FIrpic)을 홀 수송용 호스트 물질인 N,N'-dicarbazolyl-3,5-benzene (mCP)에 도핑하고, TBT와 bis(2-phenylquinolinato)-acetylacetonate iridium(III) (Ir(pq)2acac)를 전자 수송용 호스트 물질인 1,3,5-tris(N-phenylbenzimidazole-2-yl)benzene (TPBi)에 도핑하여 백색 빛을 발광하는 white organic light emitting diode (OLED)를 제작하였다. TBT를 사용하여 제작한 white OLED의 최대발광 효율과 외부 양자 효율은 각각 5.94 cd/A 과 3.23%를 나타냄을 알 수 있었다. Commission Internationale de I'Eclairage (CIE) 색 좌표의 값은 1000 nit에서 (0.34, 0.36)을 띄면서 순백색을 구현함을 확인하였다. We had synthesized a green dopant material based on the binaphthyl group, 7,7'-(2,2'dimethoxy-1,1'-binaphthyl-3,3'-diyl) bis(4-(thiophen -2-yl) benzo[e][1,2,5] thiadiazole (TBT). We also fabricated the white organic light emitting diode (OLED) with a phosphorescent blue emitter : iridium(III)bis[(4,6-di-fluoropheny)-pyridinato -N,C2]picolinate (FIrpic) doped in N,N'-dicarbazolyl-3,5-benzene (mCP) of hole transport type host material and both TBT and bis(2-phenylquinolinato)- acetylacetonate iridium(III) (Ir(pq)2acac) doped in 1,3,5-tris(N-phenylbenzimidazole -2-yl)benzene (TPBi) of electron transport type host material. As a result, the property of white OLED using TBT, which demonstrated a maximum luminous efficiency and external quantum efficiency of 5.94 cd/A and 3.23 %, respectively. It also showed the pure white emission with Commission Internationale de I'Eclairage (CIE) coordinates of (0.34, 0.36) at 1000 nit.

DPVBi/Rubrene 구조를 사용한 2-파장 방식의 백색유기발광소자의 광학적ㆍ전기적 특성에 관한 연구

오환술,조재영,최성진,강명구,윤석범 한국전기전자재료학회 2004 전기전자재료학회논문지 Vol.17 No.2

The white-light-emitting organic LED(OLED) with two-wavelength was fabricated using the DPVBi of blue emitting material and a series of orange color fluorescent dye(Rubrene) by vacuum evaporation processes. The basic structure of white-light-emitting OLED was ITO/NPB(150$\AA$)/DPVBi/Rubrene/BCP(100$\AA$)/Alq$_3$(150$\AA$)/Al(600$\AA$). We analyzed the fabricated device through the changes of the DPVBi and Rubrene layer's thickness. We obtained the white-light-emitting OLED with white color light and the CIE coordinate of the device was (0.29, 0.33) at applied voltage of 13V when the thickness of DPVBi layer was 210$\AA$ and the thickness of Rubrene layer was 180$\AA$. At a current of 100㎃/$\textrm{cm}^2$, the quantum efficiency was 0.35% and at a voltage of 20V, it was 0.405%.