SiN_x 박막에 의한 OLED 소자의 보호막 특성

주성후,Ju Sung-Hoo 한국전기전자재료학회 2006 전기전자재료학회논문지 Vol.19 No.8

We has been studied the thin film encapsulation effect for organic light-emitting diodes (OLED). To evaluate the passivation properties of the passivation layer materials, we have carried out the fabrication of green light emitting diodes with ultra violet(UV) light absorbing polymer resin, $SiO_2,\;and\;SiN_x$, respectively. From the measurement results of shrinkage properties according to the exposure time to the atmosphere, we found that $SiN_x$ thin film is the best material for passivation layer. We have investigated the emission efficiency and life time of OLED device using the package structure of $OLED/SiN_x/polymer$ resin/Al/polymer resin. The emission efficiency of this OLED device was 13 lm/W and life time was about 2,000 hours, which reach 95 % of the performance for the OLED encapsulated with metal.

C545T가 첨가된 OLED 소자의 발광특성

주성후(Sung Hoo Ju),양재웅(Jae Woong Yang) 한국표면공학회 2007 한국표면공학회지 Vol.40 No.2

To investigate the characteristics of green light-emitting OLED device, C545T material with Alq 3 was doped in the OLED device of ITO(1500)/2-TNATA(400 A)/NPB(80 A)/Alq₃:C545T(160 A)/Alq₃(240 A)/LiF(3 A)/ Al(2400 A) structure, which was used as a activator at the respective concentration of 0.5 vol.%, 1 vol.%, 2 vol.% and 3 vol.%. It was observed from the experiments that the device efficiency firstly increased with the increase of C545T concentration and the maximum efficiency of 10.9 cd/A and 4.28 ㏐/W was obtained at C545T concentration of 1 vol.%, and then the device efficiency decreased as the C545T activator concentration increased above 2 vol.% contents, while the longest lifetime of over 750 hours was obtained at C545T concentration of 1 vol.%.

OLED소자의 수명에 미치는 다층 보호막의 영향

주성후(Sung Hoo Ju),양재웅(Jae Woong Yang) 한국표면공학회 2012 한국표면공학회지 Vol.45 No.1

Multilayer passivation film on OLED with organic/inorganic hybrid structure as to diminish the thermal stress and expansion was researched to protect device from the direct damage of O2 and H2O and improve life time characteristics. Red OLED doped with 1 vol.% Rubrene in Alq3 was used as a basic device. The films consist of ITO(150 nm)/ELM200_HIL(50 nm)/ELM002_HTL(30 nm)/ Alq3: 1 vol.% Rubrene(30 nm)/Alq3(30 nm) and LiF(0.7 nm)/Al(100 nm) which were formed in that order. Using LiF/SiNx as a buffer layer was determined because it significantly improved life time characteristics without suffering damage in the process of forming passivation film. Multilayer passivation film on buffer layer didn"t produce much change in current efficiency, while the half life time at 1,000 cd/㎡ of OLED/LiF/SiNx/E1/SiNx was 710 hours which showed about 1.5 times longer than OLED/LiF/SiNx/E1 with 498 hours. futhermore, OLED/LiF/SiNx/E1/SiNx/E1/SiNx with 1301 hours showed about twice than OLED/LiF/SiNx/E1/SiNx which demonstrated that superior characteristics of life time was obtained in multilayer passivation film. Through the above result, it was suggested using LiF/SiNx as a buffer layer could reduce the damage from the difference of thermal expansion coefficient in OLED with protective films, and epoxy layer in multilayer passivation film could function like a buffer between SiNx inorganic layers with relatively large thermal stress.

2원 첨가 적색 OLED 소자의 발광특성

김경민,주성후,Kim, Kyong-Min,Ju, Sung-Hoo 한국전기전자재료학회 2007 전기전자재료학회논문지 Vol.20 No.6

To invest the luminescent characteristics of red light emitting OLED device, a dual dopant system was incorporated into the emitting layer. The multiple layer OLED device structure was $ITO(1500\;{\AA})/HIL(200\;{\AA})/a-NPD(600\;{\AA})/EML(300\;{\AA})/Alq_3(200\;{\AA})/LiF(7\;{\AA})/Al(1800\;{\AA})$. The concentrations of the rubrene dopant were tested at 0 vol.%, 3 vol.%, 6 vol.% and 9 vol.%. The maximum device efficiency and life time were obtained at the rubrene dopant concentration of 6 vol.%. Emission spectrum and color coordinate of devices showed no relationship with rubrene dopant concentration. Experiment results show that rubrene dopant absorbs energy from $Alq_3$ host and transfer it to RD1 dopant acting as an energy intermediate and influencing the device efficiency, finally the red light is emitted from the RD1 dopant.

평판 유리로 봉인된 유-무기 보호 박막을 갖는 OLED 봉지 방법

박민경,주성후,Park, Min-Kyung,Ju, Sung-Hoo 한국전기전자재료학회 2012 전기전자재료학회논문지 Vol.25 No.5

To study encapsulation method for large-area organic light emitting diodes (OLEDs), red emitting OLEDs were fabricated, on which $Alq_3$ as organic buffer layer and LiF and Al as inorganic protective layers were deposited to protect the damage of OLED by epoxy. And then the OLEDs were attached to flat glass by printing method using epoxy. The basic structure of OLED doped with rubrene of 1 vol.% as emitting layer is ITO(150 nm) / 2-TNATA(50 nm) / ${\alpha}$-NPD(30 nm) / $Alq_3$:Rubrene(30 nm) / $Alq_3$(30 nm) / LiF(0.7 nm) / Al(100 nm). In case of depositing $Alq_3$, LiF and Al and then attaching of flat glass onto OLED, current density, luminance, efficiency and driving voltage were not changed and lifetime was increased according to thickness of Al as inorganic protective layers. The lifetime of OLED/$Alq_3$/LiF/Al_4/glass structure was 139 hours increased by 15.8 times more than bare OLED of 8.8 hours and 1.6 times more than edge sealed OLED of 54.5 hours.

교류 구동 방법에 의한 유기전계발광소자 발광 특성의 모델

서정현,주성후,Seo, Jung Hyun,Ju, Sung Hoo 한국재료학회 2021 한국재료학회지 Vol.31 No.10

This paper proposes a mathematical model that can calculate the luminescence characteristics driven by alternating current (AC) power using the current-voltage-luminance (I-V-L) properties of organic light emitting devices (OLED) driven by direct current power. Fluorescent OLEDs are manufactured to verify the model, and I-V-L characteristics driven by DC and AC are measured. The current efficiency of DC driven OLED can be divided into three sections. Region 1 is a section where the recombination efficiency increases as the carrier reaches the emission layer in proportion to the increase of the DC voltage. Region 2 is a section in which the maximum luminous efficiency is stably maintained. Region 3 is a section where the luminous efficiency decreases due to excess carriers. Therefore, the fitting equation is derived by dividing the current density and luminance of the DC driven OLED into three regions, and the current density and luminance of the AC driven OLED are calculated from the fitting equation. As a result, the measured and calculated values of the AC driving I-V-L characteristics show deviations of 4.7% for current density, 2.9 % for luminance, and 1.9 % for luminous efficiency.

소자 구조에 따른 형광 OLED의 Impedance 특성

공도훈,주성후,Kong, Do-Hoon,Ju, Sung-Hoo 한국재료학회 2018 한국재료학회지 Vol.28 No.1

To study the impedance characteristics of a fluorescent OLED according to the device structure, we fabricated Device 1 using ITO / NPB / $Alq_3$ / Liq / Al, Device 2 using ITO / 2-TNATA / NPB / $Alq_3$ / Liq / Al, and Device 3 using ITO / 2-TNATA / NPB / SH-1:BD / $Alq_3$ / Liq / Al. The current density and luminance decreased with an increasing number of layers of the organic thin films in the order of Device 1, 2, 3, whereas the current efficiency increased. From the Cole-Cole plot at a driving voltage of 6 V, the maximum impedance values of Devices 1, 2, and 3 were respectively 51, 108, and $160{\Omega}$ just after device fabrication. An increase in the impedance maximum value is a phenomenon caused by the charge mobility and the resistance between interfaces. With the elapse of time after the device fabrication, the shape of the Cole-Cole plot changed to a form similar to 0 or a lower voltage due to the degradation of the device. As a result, we were able to see that an impedance change in an OLED reflects the characteristics of the degradation and the layer.

평판 유리로 봉인된 다층 무기 박막을 갖는 OLED 봉지 방법

박민경,주성후,양재웅,백경갑,Park, Min-Kyung,Ju, Sung-Hoo,Yang, Jae-Woong,Paek, Kyeong-Kap 한국전기전자재료학회 2011 전기전자재료학회논문지 Vol.24 No.11

To study encapsulation method for large-area organic light emitting diodes (OLEDs), red emitting OLEDs were fabricated, on which LiF and Al were deposited as inorganic protective films. And then the OLED was attached to flat glass by printing method using epoxy. In case of direct coating of epoxy onto OLED by printing method, luminance and current efficiency were remarkably decreased because of the damage to the OLED by epoxy. In case of depositing LiF and Al as inorganic protective films and then coating of epoxy onto OLED, luminance and current efficiency were not changed. OLED lifetime was more increased through inorganic protective films between OLED and flat glass than that without any encapsulation (8.8 h), i.e., 47 (LiF/Al/epoxy/glass), 62 (LiF/Al/LiF/epoxy/glass), and 84 h (LiF/Al/Al/epoxy/glass). The characteristics of OLED encapsulated with inorganic protective films (attached to flat glass) showed the possibility of application of protective 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.

형광과 인광 첨가제에 의한 적색 OLED 소자의 발광 특성

박연석,양재웅,주성후,Park, Yeon-Suk,Yang, Jae-Woong,Ju, Sung-Hoo 한국전기전자재료학회 2009 전기전자재료학회논문지 Vol.22 No.12

Red color OLED has been fabricated by the doping method apply to CBP using co-evaporation, GDI4349 of phosphorescent dopant, and rubrene of fluorescent dopant. The OLED structure are multi-layer of ITO(150 nm)/ELM_HIL(50 nm)/ELM_HTL(30 nm)/CBP : Rubrene, GDI4349 (30 nm)/BAlq (30 nm)/LiF(0.7 nm)/Al (100 nm). Accomplished best result at 3 vol.% of rubrene when the OLEDs were made of 1, 3, 5, 7, 9 vol.% doped rubrene. The highest efficiency of 7.2 cd/A was resulted at 8 vol.% of GDI4349 when the OLEDs were made among 5, 8, 11, 14 vol.% of GDI4349. Obviously, the best concentration of rubrene at 3 vol.% and changing GDI4349 concentration to 5, 8, 11, 14 vol.% OLED dramatically enhanced characteristic of resulted 10.7 cd/A at 8 vol.% of GDI4349. This result would understand to analyse as the emission efficiency increases by energy transport efficiency increase using GDI4349 energy transfer when rubrene absorbs the energy from CBP of fluorescences host.