過濾製程及熱處理對MEH-PPV有機發光二極體光電特性的影響

簡易檢索 / 詳目顯示

回結果列表

研究生：	梁義忠 Yi-Chung Liang
論文名稱：	過濾製程及熱處理對MEH-PPV有機發光二極體光電特性的影響 Effects of Filtration Process and Thermal Treatment on Optoelectronic Characteristics of MEH-PPV Polymer Light-Emitting Diodes
指導教授：	洪志旺 Jyh-Wong Hong
口試委員:
學位類別：	碩士 Master
系所名稱：	資訊電機學院 - 電機工程學系 Department of Electrical Engineering
畢業學年度：	94
語文別：	英文
論文頁數：	86
中文關鍵詞：	有機發光二極體、熱處理、未過濾、高分子材料、玻璃基板、塑膠基板
外文關鍵詞：	PLED, polymer, polymer material, MEH-PPV, thermal treatment, filtration process, glass substrate, plastic substrate
相關次數：	點閱：26 下載：0
分享至:	分享至facebook 分享至twitter

查詢本校圖書館目錄查詢臺灣博碩士論文知識加值系統勘誤回報

摘?要
現今顯示器技術蓬勃發展，可應用於次世代顯示面版的有機發光二極體（OLED）已成為最具發展潛力的項目之一。其中高分子發光二極體（PLED）更具有製程簡單，成本低等優點。與小分子發光二極體比較，高分子發光二極體目前有操作電壓較高，發光效率較低，電極介面較差等問題。
本研究的主要目的是利用熱處理的方法來改善高分子發光二極體的缺點，並且探討未過濾的高分子材料溶液對元件發光效率的影響。實驗結果顯示，無論高分子發光二極體製作在玻璃基板或塑膠基板上，適當的熱處理確實可降低元件操作電壓，提高其發光效率，大幅改善元件的光電特性。另外，在元件製程中如使用未過濾高分子材料溶液可增加電子電洞的復合率，當外加電壓上升至一臨界電壓時，發現元件亮度有突然增加的現象。
利用適當的製程及熱處理方法，在玻璃基板上可獲得最佳的元件亮度高達436,000 cd/m2，其頻譜峰值為592 nm，電激光臨界電壓為6.4 V；在塑膠基板上最佳的元件亮度可達43,600 cd/m2，電激光臨界電壓為8.5 V，可忍受的曲率半徑達2 cm。

Abstract
Since the thermal treatment (or annealing) is an important technique to control the morphology of poly(2-methoxy-5-(2’ethylhexoxy)-1, 4-phenylene-vinylene) (MEH-PPV) film, it has been employed in this study to improve the performances of MEH-PPV-based PLEDs fabricated on the glass or plastic substrate. The optimal thermal treatment condition could reduce the electroluminescence (EL) threshold voltage and enhance the brightness of a PLED. Also, the unfiltered powders of dissolved MEH-PPV played an important role affecting the device performance. They would confine the carriers and hence the recombination rate of electron-hole pairs could be enhanced. With the proper filtration process and thermal treatment condition, the device obtainable on glass substrate had a brightness (luminance efficiency) of 436,000 cd/m2 (130 cd/A) at an injection current density of 355 mA/cm2, and an EL threshold voltage of 6.4 V. Also, the device obtainable on plastic substrate had a brightness (luminance efficiency) of 43,600 cd/m2 (7.11 cd/A) at an injection current density of 600 mA/cm2, and an EL threshold voltage of 8.5 V.

Chapter 1	INTRODUCTION…………………………………………………………………………1
Chapter 2	EXPERIMENTAL PROCEDURES……………………………………………………………5
1	Preparation of conjugated polymer………………………………………………5
1.1	Characteristics of MEH-PPV………………………………………………………5
1.2	Selection of solvent………………………………………………………………7
1.3	Preparation of MEH-PPV solution…………………………………………………8
2	Selection of plastic substrate…………………………………………………8
3	Spin-coating System…………………………………………………………………9
4	Thermal evaporation system………………………………………………………12
5	Radio-frequency sputtering system……………………………………………12
6	Device synopsis……………………………………………………………………14
7	Device fabrications………………………………………………………………14
7.1	PLEDs on ITO-coated glass substrate…………………………………………14
7.2	PLEDs on plastic substrate………………………………………………………15
8	Measurement techniques……………………………………………………………16
8.1	Sheet resistance……………………………………………………………………16
8.2	Optical band-gap of conjugated polymer film………………………………17
8.3	EL intensity and brightness……………………………………………………21
8.4	EL spectrum…………………………………………………………………………21
8.5	FTIR spectrum.………………………………………………………………………21
Chapter 3	RESULTS AND DISCUSSION……………………………………………………………24
1	Thickness variation with different spin speeds……………………………24
2	Thermal treatment of PLEDs on glass…………………………………………28
2.1	Effects of annealing temperature………………………………………………28
2.2	Effects of annealing time………………………………………………………32
2.3	Effects of different thermal treatment processes…………………………32
2.4	FTIR spectrum………………………………………………………………………45
2.5	EL and PL spectra…………………………………………………………………45
2.6	Comparison of different concentrations………………………………………53
3	Thermal treatment of PLEDs on PET substrate………………………………53
3.1	Effect of thermal treatment on sheet resistance of ITO film…………53
3.2	Effects of annealing temperature………………………………………………56
4	Current-conduction mechanism……………………………………………………61
4.1	Ideality factor……………………………………………………………………61
4.2	Low electric-field region………………………………………………………61
4.3	High electric-field region………………………………………………………62
Chapter 4	CONCLUSION……………………………………………………………………………65
REFERENCES………………………………………………………………………………………67

                                

REFERENCES
[1] C. K. Chiang, C. R. Fischer, Y. W. Park, and A. J. Heeger, “Electrical Conductivity in Doped Polyacetylend,” Phys. Rev. Lett., Vol. 39, No. 17, pp. 1098-1101, 1977.
[2] M. Pope, H. P. Kallmann, and P. Magnante, “Electroluminescence in Organic Crystals,” J. Chem. Phys., Vol. 38, pp. 2042-2043, 1963.
[3] W. Helfrich and W. G. Schneider, “Recombination Radiation in Anthracene Crystals,” Phys. Rev. Lett., Vol. 14, No. 7, pp. 229-231, 1965.
[4] C. W. Tang and S. A. VanSlyke, “Organic Electroluminescent Diodes,” Appl. Phys. Lett., Vol. 51, No. 12, pp.913-915, 1987.
[5] J. H. Burroughes, D. D. C. Bradley, A. R. Brown, R. N. Marks, K. Mackley, R. H. Friend, P. L. Burn, and A. B. Holmes, “Light-Emitting Diodes Based on Conjugated Polymers,” Nature, Vol. 347, pp. 539-541, 1990.
[6] K. S. Fang, “Polymer Light-Emitting Diodes with Composition-Graded Amorphous Silicon-Alloy Electron Injection and Hole Buffer Layers,” M. S. Thesis, NCU, Taiwan, R.O.C., 2004.
[7] G. Gustafsson, Y. Cao, G. M. Treacy, F. Klavetter, N. Colaneir, and A. J. Heeger, “Flexible Light-Emitting Diodes Made from Soluble Conducting Polymers,” Nature, Vol. 357, pp. 477-479, 1992.
[8] P. E. Burrows, G. Gu, V. Bulović, Z. Shen, S. R. Forrest, and M. E. Thompson, “Achieving Full-Color Organic Light-Emitting Devices for Lightweight, Flat-Panel Displays,” IEEE Trans. on Electron Devices, Vol. 44, No. 8, pp. 1188-1203, 1997.
[9] A. Sugimoto, H. Oshi, S. Fujimura, A. Yoshida, T. Miyadera, and Tsuchida, “Flexible OLED Displays Using Plastic Substrates,” IEEE J. Quantum Electronics, Vol. 10, No. 1, pp.107-114, 2004.
[10] G. Hadziioannou and P. F. van Hutten, “Semiconducting Polymers,” chap. 1, pp. 4-6, 2000.
[11] D. Braun and A. J. Heeger, “Visible Light Emission from Semiconducting Polymer Diodes,” Appl. Phys. Lett., Vol. 58, No. 18, pp. 1982-1984, 1991.
[12] X. Y. Deng, W. M. Lau, K. Y. Wong, K. H. Low, H. F. Chow, and Y. Cao, “High Efficiency Low Operating Voltage Polymer Light-Emitting Diodes with Aluminum Cathode,” Appl. Phys. Lett., Vol. 84, No. 18, pp. 3522-3524, 2004.
[13] X. Y. Deng, L. P. Zheng, G. Yu, and Y. Cao, “Polymer Heterojunction Photodiodes with MEH-PPV doped with organic acceptors,” Synthetic Metals, Vol. 135-136, pp. 823-824, 2003.
[14] J. L. Kim, J. K. Kim, H. N. Cho, D. Y. Kim, and S. I. Hong, “Polyquinoline Copolymers as Electron Transporting Layer in Light-Emitting Diodes,” Synthetic Metals, Vol. 114, pp. 97-100, 2000.
[15] C. S. Lin, R. H. Yeh, C. P. Huang, and J. W. Hong, “Optoelectronic Characteristics of Polymer Light Emitting Diodes with Poly(2-methoxy-5-(2’ethyl-hexoxy)-1,4-phenylene-vinylene) and Hydrogenated Amorphous Silicon Alloy Heterointerfaces,” Appl. Phys. Lett., Vol. 81, No. 2, pp. 205-207, 2002.
[16] J. H. Park, O O. Park, J. W. Yu and J. K. Kim, and Y. C. Kim, “Effect of Polymer-Insulating Nanolayers on Electron Injection in Polymer Light-Emitting Diodes,” Appl. Phys. Lett., Vol. 84, No. 10, pp. 1783-1785, 2004.
[17] J. Kim, J. Lee, C. W. Han, N. Y. Lee, and I. J. Chung, “Effect of Thermal Annealing on the Lifetime of Polymer Light-Emitting Diodes,” Appl. Phys. Lett., Vol. 82, No. 24, pp. 4238-4240, 2003.
[18] C. P. Liu and Y. T. Hung, “The Effect of Thermal Annealing and Evaporating Vacuum Level on the Performance of a Polyfluorene-based Polymer Light Emitting Diode,” Thin Solid Films, Vol. 492, pp. 269-274, 2005.
[19] M. I. Sluch, C. Pearson, M. C. Petty, M. Halim, and I. D. W. Samuel, “Photo- and Electroluminescence of Poly (2-methoxy, 5- (2’- ethylheloxy)-p-phenylene vinylene) Langmuir-Blodgett Films,” Synthetic Metals, Vol. 94, pp. 285-289, 1998.
[20] H. Zhang, X. Lu, Y. Li, X. Ai, X. Zhang, and G. Yang, “Conformational Transition of poly[2-methoxy-5-(2’-ethylhexoxy)- p-phenylene vinylene] in Solutions: Solvent-Induced Emitter Change,” Journal of Photochemistry and Photobiology A: Chemistry, Vol. 147, pp. 15-23, 2002.
[21] Y. Liu, M. S. Liu, X. C. Li, and A. K. Y. Jen, “Synthesis and Characterization of a Novel Light-Emitting Polymer Containing Highly Efficient Hole-Transporting Aromatic Diamine,” Chem. Mater., Vol. 10, pp. 3301-3304, 1998.
[22] C. P. Huang, “Optoelectronic Characteristics of a-SiN:H-Based TFLEDs and Organic LEDs,” M. S. Thesis, NCU, Taiwan, R.O.C., 2000.
[23] J. Liu, Y. Shi, L. Ma, and Y. Yang, “Device Performance and Polymer Morphology in Polymer Light Emitting Diodes: The Control of Device Electrical Properties and Metal/Polymer Contact,” J. Appl. Phys., Vol. 88, No. 2, pp. 605-609, 2000.
[24] I. D. Parker, “Carrier Tunneling and Device Characteristics in Polymer Light-Emitting Diodes,” J. Appl. Phys., Vol. 75, No. 3, pp. 1656-1666, 1994.
[25] J. Tauc, “Amorphous and Liquid Semiconductors,” chap. 5, Plenum Press, PP. 175, 1974.
[26] S. Walheim, M. Boltau, Jurgen Mlynek, G. Krausch, and Ullrich Steiner, “Structure Formation via Polymer Demixing in Spin-Cast Films,” Macromolecules, vol. 30, pp. 4995-5003, 1997.
[27] Y. Shi, J. Liu, and Y. Yang, “Device Performance and Polymer Morphology in Polymer Light Emitting Diodes: The Control of Thin Film Morphology and Device Quantum Efficiency,” J. Appl. Phys., Vol. 87, No. 9, pp. 4254-4263, 2000.
[28] 陳金鑫、黃孝文，“OLED有機電激發光材料與元件”，五南圖書出版股份有限公司，2005年9月，ISBN：957-11-4056-2.
[29] T. W. Lee, O. O. Park, L. M. Do, and T. Zung, “Improvement of EL Efficiency in Polymer Light-Emitting Diodes by Heat Treatments,” Synthetic Metals, Vol. 117, pp. 249-251, 2001.
[30] S. A. Arnautov, E. M. Nechvolodova, A. A. Bakulin, S. G. Elizarov, and A. N. Khodarev, “Properites of MEH-PPV Films Prepared by Slow Solvent Evaporation,” Synthetic Metals, Vol. 147, pp. 287-291, 2004.
[31] T. W. Lee and O O. Park, “The Effect of Different Heat Treatments on the Luminescence Efficiency of Polymer Light-Emitting Diodes,” Advanced Materials, Vol. 12, No. 11, pp. 801-804, 2000.
[32] M. Atreya, S. Li, E. T. Kang, K. G. Neoh, Z. H. Ma, K. L. Tan, and W. Huang, “Stability Studies of poly92-methoxy-5-(2’-ethyl hexyloxy)-p-(phenylene vinylene) [MEH-PPV],” Polymer Degradation and Stability, Vol. 65, pp. 287-296, 1999.
[33] 李匡邦、許東明、何東英，“光譜化學分析”，揚智文化事業股份有限公司，1997年9月，ISBN：957-8446-22-5.
[34] J. Liu, T. F. Guo, and Y. Yang, “Effect of Thermal Annealing on the Performance of Polymer Light Emitting Diodes,” J. Appl. Phys., Vol. 91, No. 3, pp. 1595-1600, 2002.
[35] Gregory P. Crawford, “Flexible Flat Panel Displays,” chap. 5, John Wiley & Sons, 2005, ISBN: 0-470-87048-6.
[36] S. H. Kwon, S. Y. Paik, and J. S. Yoo, “Electroluminescent Properties of MEH-PPV Light-Emitting Diodes Fabricated on the Flexible Substrate,” Synthetic Metals, Vol. 130, pp. 55-60, 2002.
[37] Y. Li, L. W. Tan, Z. T. Hao, K. S. Ong, and F. Zhu, “Flexible Top-Emitting Electroluminescent Devices on Polyethylene Terephthalate Substrates,” Appl. Phys. Lett., Vol. 86, No. 153508, pp. 1-3, 2005.
[38] P. W. M. Blom, M. J. M. de Jong, and J. J. M. Vleggaar, “Electron and Hole Transport in poly(p-phenylene vinylene) Devices,” Appl. Phys. Lett. Vol. 68, No. 23, pp. 3308-3310, 1996.
[39] A. J. Campbell, D. D. C. Bradley, and D. G. Lidzey, “Space-Charge Limited Conduction with Traps in poly(phenylene vinylene) Light Emitting Diodes,” J. Appl. Phys., Vol. 82, No. 12, pp. 6326-6342, 1997.
[40] M. Zhu, T. Cui, K. Varahramyan, “Experimental and Theoretical Investigation of MEH-PPV-based Schottky Diodes,” Microelectronic Engineering, Vol. 75, pp. 269-274, 2004.
[41] M. A. Lampert and P. Mark, “Current Injection in Solids,” chap. 2, 4, 5, Academic Press, 1970.

簡易檢索 / 詳目顯示

相關論文