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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.
김정택,백경갑,주성후,Kim, Jung-Taek,Paek, Kyeong-Kap,Ju, Sung-Hoo 한국전기전자재료학회 2009 전기전자재료학회논문지 Vol.22 No.11
The characteristics of organic films can be affected by the temperature of evaporation source because the temperature of evaporation source has an effect on substrate temperature during OLED fabrication process using the thermal evaporation. To investigate the characteristics of OLED devices fabricated by using thermally damaged organic films, I-V-L and half life-time in OLED devices fabricated with various substrate temperatures were measured. During emission layer(EML) evaporation, OLED devices with a structure of ITO(100 nm)/ELM200(50 nm)/NPB(30 nm)/$Alq_3$(55 nm)/LiF(0.7 nm)/Al(100 nm) were fabricated at various substrate temperatures(room temperature, $30^{\circ}C$, $40^{\circ}C$, and $50^{\circ}C$). The characteristics of current density and luminance versus applied voltage in OLED devices fabricated shows that many electrical currents flowed and high brightness appeared at low voltage, but that the lifetime of OLED devices dropped suddenly. This phenomenon explained that the crystallization of $Alq_3$ thin film appeared owing to the substrate heating during evaporation.
청색 활성제의 첨가 형상 변화에 따른 백색 OLED의 발광 특성
임병관,서정현,백경갑,주성후,Lim, Byung-Gwan,Seo, Jung-Hyun,Paek, Kyeong-Kap,Ju, Sung-Hoo 한국전기전자재료학회 2011 전기전자재료학회논문지 Vol.24 No.6
To investigate the effect of two-emission-layer structure on the emission characteristics of the phosphorescent white organic light-emitting diodes (PHWOLEDs), the PHWOLEDs with two different emission layers, blue EML(29 nm, FIrpic-doped mCP) and red EML(1 nm, Ir(pq)$_2$acac-doped CBP)), following host-guest system were fabricated. The bi-layered blue EML was composed of mCP:FIrpic (20 nm, 7 vol.%) and mCP:FIrpic (9 nm, 7, 10, 15, 20, and 25 vol.%, respectively). When the concentration of FIrpic was increased from 7 to 15 vol.%, light emission luminance, current efficiency, and external quantum efficiency were increased. On the contrary, when the concentration of FIrpic was increased to more than 20 vol.%, light emission luminance, current efficiency, and external quantum efficiency were decreased. The PHWOLEDs with the bi-layered blue EML structure of mCP:FIrpic (20 nm, 7 vol.%) and mCP:FIrpic (9 nm, 15 vol.%) showed current efficiency of 29.7 cd/A and external quantum efficiency (EQE) of 16.6% at 1,000 $cd/cm^2$.
서정현,양재웅,백경갑,주성후,Seo, Jung-Hyun,Yang, Jae-Woong,Paek, Kyeong-Kap,Ju, Sung-Hoo 한국표면공학회 2019 한국표면공학회지 Vol.52 No.2
To study the characteristics of AC driven OLED, we fabricated the fluorescent OLEDs and analyzed the electroluminescence characteristics of OLEDs with AC negative voltage. The luminance and the current density of the OLED decreased, and the number and size of the dark spots increased in proportion to the duration time and level of the applied AC negative voltage. The current efficiency of the OLED was improved when high AC negative voltage was applied within a short time. When the AC negative voltage of 10 V was applied for 1 minute, the efficiency was improved by 12.4%. Also, the degradation of luminance and current efficiency due to the duration of light emission was improved in the case of OLED applied for 1 minute with 10 V AC negative voltage. These are expected as a result of the improvement of the leakage current characteristics by eliminating the short-circuit region formed by the defect of the OLED at the AC negative high voltage. As a result, the continuous application of AC negative voltage reduced the luminance and the current density of OLED, but the temporary application of AC negative voltage with the proper time and voltage could improve the efficiency and lifetime of OLED.
임병관,서정현,주성후,백경갑,Lim, Byung-Gwan,Seo, Jung-Hyun,Ju, Sung-Hoo,Paek, Kyeong-Kap 한국전기전자재료학회 2010 전기전자재료학회논문지 Vol.23 No.12
In order to investigate the emission characteristics of the phosphorescent white organic light-emitting diodes (PHWOLEDs) according to various hole transport layers (HTLs), PHWOLEDs composed of HTLs whose structure are NPB/TCTA, NPB/mCP and NPB/TCTA/mCP, two emissive layers (EMLs) which emit two-wavelengths of light (blue and red), and electron transport layer were fabricated. The applied voltage, power efficiency, and external quantum efficiency at a current density of $1 mA/cm^2$ for the fabricated PHWOLEDs were 7.5 V, 11.5 lm/W, and 15%, in case of NPB/mCP, 5 V, 14.8 lm/W, and 13.7%, in case of NPB/TCTA, and 5.5 V, 14.6 lm/W, and 15%, in case of NPB/TCTA/mCP in the hole transport layer, respectively. High emission efficiency can be obtained when the amount of hole injection from anode is balanced out by the amount of electron injection from the cathode to EML by using NPB/TCTA/mCP structured HTL.
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.
이봉섭,고신위,박종억,백용구,양재웅,백경갑,주성후,Lee, Bong-Sub,Gao, Xin-Wei,Park, Jong-Yek,Baek, Yong-Gu,Yang, Jae-Woong,Paek, Kyeong-Kap,Ju, Sung-Hoo 한국전기전자재료학회 2008 전기전자재료학회논문지 Vol.21 No.6
In this paper, the hole injection layer(HIL) materials have been synthesized and analyzed. Their HOMO levels are $4.93{\sim}5.22\;eV$, and their energy band gaps are $2.74{\sim}3.19\;eV$. Their glass transition temperatures($T_g$) are all above $114^{\circ}C$, which implies that they are highly thermal-stable. The green OLED devices with a structure of ITO(150 nm)/NEW_HIL(50 nm)/NPB(30 nm)/$Alq_3$(50 nm)/Al:Li(100 nm) were fabricated and tested, incorporating these newly synthesized HIL materials. According to the test results of OLED devices, the I-V-L performances of these devices increase in the following sequence: ELM307 > ELM200 > ELM321 > ELM327 > ELM325. In addition, the OLED device with ELM307 as a HIL has the highest brightness and efficiency at the same driving voltage. These experimental results have shown that ELM307 can be used as one of the most promising candidates for HIL materials.
퍼지소속함수에 기초한 신경망을 이용한 제어기 설계에 관한 연구
백경갑 대진대학교 1995 大眞論叢 Vol.3 No.-
This paper presents a new controller design method for learning a nonlinear function existing between real plant and controller outputs in the practical dynamic systems. A new controller is based on the FMFNN(Fuzzy Membership Function based Neural Network) being able to learn nonlinear functions well. FMFNN architecture can a) enhance the capability of learning, b) obtain optimal control rules modified by learning. The proposed controller based on the FMFNN is applied to 3rd order linear system and non-linear system. Simulation results show the improved performance such as the stability, response speed, reduced tracking errors.