저일함수 금속 아세트산 화합물 층을 사용한 유기발광다이오드의 전기발광 특성 향상

김만수; 류근채; 김영철; Mansu Kim; Geun-Chae Yu; Young Chul Kim

Korean Chemical Engineering Research, Vol.51, No.5, 634-639, October, 2013

DOI10.9713/kcer.2013.51.5.634 Export Citation

저일함수 금속 아세트산 화합물 층을 사용한 유기발광다이오드의 전기발광 특성 향상

Effects of Low Workfunction Metal Acetate Layers on the Electroluminescent Characteristics of Organic Light-Emitting Diodes

김만수, 류근채, 김영철 ^†

경희대학교 화학공학과, 446-701 경기도 용인시 기흥구 서천동 1

Mansu Kim, Geun-Chae Yu, and Young Chul Kim^†

Department of Chemical Engineering, Kyung Hee University, 1 Seocheon-dong, Giheung-gu, Yongin-si, Gyeonggi 446-701, Korea

E-mail:

초록

유기발광다이오드(Organic Light-Emitting Diodes, OLEDs)의 효율을 향상시키기 위하여 다양한 아세트산금속(Macetate, M: Li, Na, K, Cs)을 cathode underlayer 소재로 사용하고 이들이 소자의 전자주입 및 발광 특성에 미치는 영향에 대하여 연구하였다. 1 nm 두께의 M-acetate 층을 cathode underlayer로 사용한 경우 Cs-acetate를 사용한 소자를 제외한 모든 소자에서 기존의 LiF 전자주입층을 사용한 소자보다 효율적인 전자주입 및 향상된 발광특성을 보였으며, M-acetate에 포함된 금속의 일함수가 작을수록 높은 전류밀도와 우수한 발광특성을 보였다. 또한, cathode underlayer 의 두께가 소자의 특성에 미치는 영향을 분석한 결과, 사용된 M-acetate의 분자크기에 따라 각기 다른 두께(Li-acetate 0.7 nm, Cs-acetate 2.0 nm)에서 최적의 발광특성을 보였으며 기존의 LiF 층을 사용한 소자에 비하여 동일 인가전압에서 전류효율이 약 60% 향상된 결과를 얻을 수 있었다.

We investigated the effects of a cathode underlayer on the electroluminescence (EL) characteristics of organic light-emitting diodes (OLEDs) using various metal acetates (M-acetate, M = Li, Na, K, Cs) as a cathode underlayer. When 1 nm thick M-acetate layers were used as a cathode underlayer, the OLEDs with M-acetate showed better EL performance than the device with the conventional LiF electron injection layer except the device with Cs-acetate. More enhanced current density and improved EL characteristics were obtained when lower work function metal acetate was employed. In addition, the optimum M-acetate layer thickness that gives the best device performance proved to be 0.7 and 2.0 nm for Li-acetate and Cs-acetate, respectively, probably depending on the molecular size of M-acetate. The OLEDs with the M-acetate layers of optimized thickness demonstrated more than 60% enhanced current efficiency compared with that of the device using an LiF layer at the same applied voltage.

Keywords:OLED;Cathode Underlayer;Work Function;Metal Acetate;Electron Injection

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[2] Stossel M, Staudigel J, Steuber F, Simmerer J, Winnacker A, Appl. Phys. A., 68, 387 (1999)

[3] Hung LS, Tang CW, Mason MG, Appl. Phys. Lett., 70, 152 (1997)

[4] Zhang ST, Ding XM, Zhao JM, Shi HZ, He J, Xiong ZH, Ding HJ, Obbard EG, Zhan YQ, Huang W, Hou XY, Appl. Phys. Lett., 84(3), 425 (2004)

[5] Hung LS, Zhang RQ, He P, Mason G, J. Phys. D Appl. Phys., 35, 103 (2002)

[6] Jabbour GE, Kippelen B, Armstrong NR, Peyghambarian N, Appl. Phys. Lett., 73, 1185 (1998)

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[11] Chan MY, Lai SL, Fung MK, Lee CS, Lee ST, J. Appl. Phys., 95, 5397 (2004)

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