旋轉塗佈及熱蒸鍍技術製作具雙電洞傳輸層之可撓式有機發光二極體

Double Hole Transport Layers Deposited by Spin-Coating and Thermal-Evaporating for Flexible Organic Light Emitting Diodes

陳信良(Shin-Liang Chen)

指導教授 ： 莊賦祥

共同指導教授 ： 蔡裕勝

國立虎尾科技大學/電機資訊學院/光電與材料科技研究所/碩士(2007年)

https://doi.org/10.6827/NFU.2007.00020

摘要

本論文以元件結構PET/ ITO (160 nm)/ NPB (41 nm)/ Alq3 (67-x nm)/ Bpy-OXD (x nm)/ LiF (0.5 nm)/ Al (135 nm)利用電子傳輸材料1,3-Bis[2-(2,2'-bipyridine-6-yl)-1,3,4-oxadiazo-5-yl]benzene (Bpy-OXD)取代部分的電子傳輸層Tris(8-hydroxy-quinolinato)aluminium (Alq3)來提昇元件效率及壽命，它具有電洞阻隔能力和電子傳輸能力，可以使元件在低電流密度時即有較高的發光效率，且利用Bpy-OXD來取代部分的Alq3可以提高元件壽命約162 %。
本論文再利用旋轉塗佈N,N'-Bis(naphthalen-1-yl)-N,N'-bis(phenyl)-benzidine (NPB)以及NPB與N,N’-diphenyl-N,N’-bis(1-naphthyl)-1,1’biphenyl-4,4’’diamine (α-NPD)共摻雜來沈積電洞傳輸材料於ITO塑膠基板上，其後再利用熱蒸鍍方式沈積NPB以製作具雙電洞傳輸層之可撓式有機發光二極體，可以改善基板表面的不平整及共摻雜濃度的精確性。元件結構為PET/ ITO (160 nm)/ HTL/ Alq3 (52 nm)/ Bpy-OXD (15 nm)/ LiF (0.5 nm)/ Al (135 nm)，此種雙電洞傳輸層結構之元件其發光亮度及效率均可獲得提昇。當電洞傳輸層為spin NPB+THF (37 nm)/ evaporate NPB (41 nm)時，最大亮度為3568 cd/m2及最大發光效率為3.86 cd/A；當電洞傳輸層為spin (NPB:α-NPD)+THF (58 nm)/ evaporate NPB (41 nm)時，最大亮度為4634 cd/m2及最大發光效率為4.18 cd/A。
本論文以元件結構為PET/ ITO (160 nm)/ NPB (41 nm)/ Alq3 (67 nm)/ LiF (0.5 nm)/ Al (135 nm)/ passivation，利用熱蒸鍍無機薄膜或有機薄膜作為可撓式有機發光二極體的薄膜封裝，其中無機薄膜採用電子注入材料LiF，而有機薄膜採用電洞注入材料4,4',4'-Tris(N-3-methylphenyl-N-phenyl-amino)triphenylamine (m-MTDATA)或是在蒸鍍薄膜後再使用的沒有ITO的空白PET塑膠片作為封裝蓋板。由實驗結果可知，利用多層封裝m-MTDATA (500 nm)/ PET比未封裝之元件可以提高壽命約545.85 %。

關鍵字

旋轉塗佈 ； 雙電洞傳輸層 ； 可撓式 ； 共摻雜 ； 有機發光二極體 ； 壽命

並列摘要

This study used the device’s structures of PET/ ITO (160 nm)/ NPB (41 nm)/ Alq3 (67-x nm)/ Bpy-OXD (x nm)/ LiF (0.5 nm)/ Al (135 nm), and the electron transport material 1,3-Bis[2-(2,2'-bipyridine-6-yl)-1,3,4-oxadiazo-5-yl]
benzene (Bpy-OXD) to substitute a part of the electron transport layer of Tris(8-hydroxy-quinolinato)aluminium (Alq3), to upgrade the efficiency and lifetime of the device having hole blocking and electronic transport capabilities to enable higher luminance efficiency in low current density, its half-lifetime will also increase about 162 % .
This study reuse the spin-coating N,N'-Bis(naphthalen-1-yl)- N,N'-bis(phenyl)-benzidine (NPB) and NPB:N,N’-diphenyl- N,N’-bis(1-naphthyl)-1,1’ biphenyl-4,4’’diamine (α-NPD) co-doped to deposit hole transport material on ITO plastic substrate in proper order thermal-evaporating to deposit NPB on ITO substrate to make flexible organic light emitting diodes (FOLED) with double hole transport layer to improve the level and smoothness of the surface of the substrate and the accuracy of the concentration of co-doped. The device’s structures are PET/ ITO (160 nm)/ HTL/ Alq3 (52 nm)/ Bpy-OXD (15 nm)/ LiF (0.5 nm)/ Al (135 nm), the luminance and luminance efficiency of the device of the double hole transport layer can both be improved. When the hole transport layer is spun NPB+THF (37 nm)/ evaporate NPB (41 nm), the maximum luminance was 3568 cd/m2 at 93.9 mA/cm2, and the maximum luminance efficiency is 3.86 cd/A at 8 V； when the hole transport layer is spun (NPB:α-NPD)+THF (58 nm)/ evaporate NPB (41 nm), the maximum luminance is 4634 cd/m2 at 9 V, and the maximum luminance efficiency is 4.18 cd/A at 68 mA/cm2.
This study used the device’s structures of PET/ ITO (160 nm)/ NPB (41 nm)/ Alq3 (67 nm)/ LiF (0.5 nm)/ Al (135 nm)/ passivation, by using the sealing of thermal evaporate inorganic film or organic film of flexible organic light emitting diodes. In which the inorganic film used the electron inject material LiF, and the organic film used the hole inject material 4,4',4'-Tris(N-3-methylphenyl-N-phenyl-amino)triphenylamine (m-MTDATA) or use the sealing lid by PET plastic without ITO after evaporating the sealing film. As a result, use a multi-layer sealing of m-MTDATA (500 nm)/ PET which its half-lifetime will increase by about 545.85 %, when compared with the non-encapsulate device.

並列關鍵字

spin-coating ； co-doping ； double hole transport layer ； lifetime ； organic light emitting diodes ； flexible

參考文獻

[1] C. Hosokawa, H. Higashi, T. Kusumoto, “Novel structure of organic electroluminescence cells with conjugated oligomers,” Appl. Phys. Lett., vol. 62, pp. 3238-3240, 1993.

[2] M. A. Baldo, V. G. Kozlov, P. E. Burrows, S. R. Forrest, V. S. Ban, B. Koene, and M. E. Thompson, “Low pressure organic vapor phase deposition of small molecular weight organic light emitting device structures,”Appl. Phys. Lett., vol. 71, pp. 3033-3035, 1997.

[3] M. Suzuki, T. Hatakeyama, S. Tokito, and F. Sato, ”High-efficiency white phosphorescent polymer light-emitting devices,” IEEE J. Select. Topics Quantum Electron., vol. 10(1), pp. 115-120, 2004.

[4] G. Gu, P. E. Burrows, S. Venkatesh, and S. R. Forrest, “Vacuum deposited, nonpolymeric flexible organic light emitting device,” Opt. Lett., vol. 22, pp. 172-174, 1997.

[5] D. Pribat and F. Plais, ”Matrix addressing for organic electroluminescent displays,” Thin Solid Films, vol. 383, pp. 25-30, 2001.