Using copper substrate to enhance the thermal conductivity

Using copper substrate to enhance the thermal conductivity...

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Using copper substrate to enhance the thermal conductivity of top-emission organic light-emitting diodes for improving the luminance efFciency and lifetime Yu-Sheng Tsai, 1, a ! Shun-Hsi Wang, 1 Chuan-Hung Chen, 1 Chien-Lung Cheng, 2 and Teh-Chao Liao 3 1 Institute of Electro-Optical and Materials Science, National Formosa University, Huwei, Yunlin 63201, Taiwan 2 Department of Electrical Engineering, National Formosa University, Huwei, Yunlin 63201, Taiwan 3 Department of Electro-Optics Engineering, National Formosa University, Huwei, Yunlin 63201, Taiwan s Received 9 October 2009; accepted 8 November 2009; published online 11 December 2009 d The infuence oF heat dissipation on the perFormances oF organic light-emitting diode s OLED d is investigated by measuring junction temperature and by calculating the rate oF heat fow. The calculated rate oF heat fow reveals that the key Factors include the thermal conductivity, the substrate thickness, and the UV glue. Moreover, the use oF copper substrate can eFFectively dissipate the joule heat, which then reduces the temperature gradient. ±inally, it is shown that the use oF a high thermal conductivity thinner substrate can enhance the thermal conductivity oF OLED and the luminance eF²ciency as well. © 2009 American Institute of Physics . f doi: 10.1063/1.3272110 g ±or the top-emission organic light-emitting diode s TEOLED d development, the luminance eF²ciency oF the de- vice was determined with the balance oF charges s electron and hole d and reduced the energy barrier between the elec- trode and organic layer. Previous papers have already re- ported many anode materials with a high work Function, such as Ag 2 O, 1 , 2 MoO x , 3 V 2 O 5 , 4 NiO x , 5 and Au. 6 In addition, in regards with the substrate, all TEOLEDs are generally Fabri- cated on the glass substrate or metal substrate. ±urthermore, the OLED Fabricated on the stainless steel substrate can im- prove the liFetime and eF²ciency oF the device. 7 In order to understand whether iF the junction temperature is too high, and may possibly cause decaying characteristics, the junction temperature measurement 8 , 9 is used to determine the junction temperature oF the device. Moreover, the eFFect oF heat dis- sipation can be illustrated by the calculated device’s rate oF heat fow. TEOLEDs are Fabricated onto glass and copper s Cu d substrates s 39 3 39 3 0.5 mm d , respectively, with Al/Au anode deposited ²rst. The hole injection layer is 4,4 8 ,4 9 -tris s N-3-methphenyl-N-phenyl-amino d -triphenyl- amine s m-MTDATA d , the hole transport layer is N,N 8 -bis s naphthalene-1-yl d -N,N 8 -bis s phenyl d -benzidine s NPB d , the emitting layer and electron transport layer is tris s 8-hydroxy- quinolinato d aluminum s Alq3 d , and the cathode is Li±/Al/Ag. A schematic TEOLED structure on diFFerent substrates was shown in the inset oF ±ig. 1 and the device active area is 25 mm 2 . ±or the TEOLED device with Cu-substrate, the UV glue is spin-coated on Cu-substrate as insulation layer. In addition, the structure oF bottom-emission s BE d OLED is glass/indium tin oxide s ITO d
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This note was uploaded on 03/27/2011 for the course CHEM 2211L taught by Professor T.a. during the Spring '08 term at University of Georgia Athens.

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Using copper substrate to enhance the thermal conductivity...

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