OLED與PLED在平面顯示器極具商業潛力，但若欲取代目前的液晶顯示器，仍有相當多的問題要解決，包括使用壽命和色澤穩定度的問題等，因此如何增加發光效率及發光亮度以延長壽命和提昇穩定度，是目前全世界在積極開發的方向。
本研究藉由加入bathophenanthroline (BPhen) 此有機層，以簡單的三層元件結構，可使元件的起始電壓降為3.6伏特(起始電壓定義為發光亮度1cd/m2時的操作電壓)，最高亮度可達到36040 cd/m2、發光效率可提升到3.32 cd/A。由於BPhen具有良好的電子傳輸及電洞阻擋效果，可使大量的電子與電洞侷限在Alq3發光層中，因此可得到一高亮度、高效率元件。
當三層元件的陽極以p-NiO改質時，元件的最高亮度可高達53600 cd/m2，最高電流密度為1.36 A/cm2，發光效率可高達4.47 cd/A。由於NiO對電洞注入有極大的幫助，電子和電洞被侷限於發光層中，可大幅增加形成”激發子(Exciton)”的機會，因此元件會有高亮度、高電流、高效率的表現。
在p型氧化鋅的製作方面，採取共摻雜的方式，在氧氣及氮氣下進行濺鍍時，將鎵及氮原子共同摻雜於氧化鋅薄膜內。當氧氣組成超過40％時，氧化鋅會由n型轉為p型，在氧氣組成為80％時，可得到最低的電阻率(5.81Ω-cm)和最高的載子濃度(1.28×1019 cm-3)。若以氧氣組成95％時的p型氧化鋅來改質ITO表面，雙層元件最高亮度為10600 cd/m2，最高電流密度則只有0.245 A/cm2，其與傳統雙層元件最高亮度(11800 cd/m2)相差不大，但電流密度(0.569 A/cm2)卻大幅減小，因此發光效率從2.07 cd/A增加到4.58 cd/A，操作電壓由原來的13伏特增加到18伏特。代表p型氧化鋅薄膜並非扮演電洞注入的角色，比較像是扮演絕緣層的角色來抑止過多電洞的注入，因此元件的效率提高而電流降低，但也同時提高操作電壓。

Although organic and polymer light-emitting diodes (OLED and PLED) exhibit great potentials in replacing LCD, many problems remain like short life time and color instability, etc. Improvements in emission efficiency and device stability will help OLED to support the market and compete with other flat panel display technologies.
In this study, organic layer, bathophenanthroline (BPhen) was inserted with simple tri-layer structure to reduce the turn on voltage from 6 volts, for the standard bi-layer structure, to 3.6 Volts. The maximum luminescence of the device could reach 36040 cd/m2 and the luminescence efficiency was raised from 1.77 cd/A to 3.32 cd/A. BPhen was able to confine electrons and holes in the emitting layer, Alq3 layer, to obtain high luminescence and luminescence efficiency because BPhen layer was a good electron transport layer as well as a good hole blocking layer.
An extremely thin p-NiO layer was employed to modify the anode in tri-layer structure and obtained very high luminescence of 53600 cd/m2. The highest current density reached was 1.36 A/cm2 and the efficiency was raised to 4.47 cd/A. NiO facilitated the hole injection and a large amount of holes were blocked in the Alq3 layer due to the high energy barrier for holes to diffuse from Alq3 to BPhen. The trapping of holes in the Alq3 layer would further induce a lot of electrons injected into the emitting layer. Therefore, the device exhibited excellent performance with a high current density, high luminescence and high luminescence efficiency.
P-type transparent conducting oxide layer showed enhance hole injection due to its high work function. P-type zinc oxide (ZnO) growth was thus attempted. When the oxygen partial pressure was below 40 %, ZnO was n-type. As the oxygen partial pressure exceeded 40%, ZnO became p-type. As PO2 reached 80 %, the lowest resistivity (5.81Ω-cm) and the highest hole concentration (1.28×1019cm-3) were obtained. Using the p-ZnO film, deposited with 95% O2 to modify the ITO surface, the maximum luminescence of bi-layer structure reached 10600 cd/m2 similar to 11800 cd/m2 for conventional bi-layer structure. The operation current density decreased from 0.569 A/cm2 to 0.0394 A/cm2 operating in 13 volts and the efficiency was raised from 2.07 cd/A to 4.58 cd/A, and the turn-on voltage increased from 13 volts to 18 volts. These indicated that the role of p-ZnO behaved more like an insulation layer than a holes injection layer. As a result, the device with the p-ZnO modified ITO exhibited low device currents and high luminescence efficiency.

1.P. Pope, H. P. Kallmann and P. J. Magnante, J. Chem. Phys., 38, 2042 (1963).
2.C. W. Tang and S. A. VanSlyke, Appl. Phys. Lett., 51, 913 (1987).
3.J. H. Burroughs, D. D. C. Bradley, A. R. Brown, R. N. Marks, K. Mackay, R. H. Friend, P. L. Burn, A. B. Holmes, Nature, 1990, 347, 359.
4.吳忠幟；光訊，第73期1998年8月.
5.李文達；液晶與顯示, 1996, 11, 155.
6.古俊能；工業材料雜誌，第169期2001年1月，p.106.
7.H. Kawazoe et al, Transparent p-type conducting oxides: design and fabrication of p-n heterojunctions, MRS Bulletin, August p.28~p.36(2000).
8.G. Mueller, Semiconductors and Semimetals, 64, 209,(New York：Academic Press) (2000).
9.黃崇傑；電子與材料，第10期，p.333.
10.H. Sato, T. Minami, S. Takata, T. Yamada, Thin Solid Film 236(1993)27.
11.林敬二；儀器分析，第五版(上冊)，p.333.
12.黃春輝著；光電功能超薄膜，北京：北京大學出版社，2001.
13.顧鴻壽著；光電有機電激發光顯示器＜技術及應用＞，2001，p.30.
14.陳壽安；光訊第79期1999年8月.
15.M. Wohlgenannt, K. Tandon, S. Mazumdar, S. Ramasesha, and Z. V. Vardeny, Nature, 409, 494 (2001).
16.Solid State Technology, P.32, March (2001).
17.S. Panozzo, M. Armand, and O. Stephan, Appl. Phys. Lett., 80, 679(2002)
18.L. C. Palilis, D. G. Lidzey, M. Redecker, D. D. C. Bradley, M. Inbasekaran, E. P. Woo, and W. W. Wu, Synth. Met., 111-112(2000)159-163
19.S. A. Vanslyke, C. H. Chen, and C. W. Tang, Appl. Phys. Lett. 69, 2160 (1996).
20.P. Fenter, F. Schreibler, V. Bulovic, and S. R. Forrest, Chem. Phys. Lett. 277, 521 (1997).
21.F. Papadimitrakopolus, X. M. Zhang, and K. A. Higginson, IEEE J. Selec.Top. Quantum Electron. 4, 49 (1998)
22.林國森，電子與材料，第8期，p.124.
23.M. B. Huang, K. McDonald, J. C. Keay, Y. Q. Wang, S. J. Rosenthal, R. A. Weller, L. C. Feldman, Appl. Phys. Lett. , 1998, 73, 2914.
24.Z. B. Deng, X. M. Ding, S. T. Deng, W. A. Gambling, Appl. Phys. Lett. , 1999, 74, 2227.
25.Y. Shirota, Y. Kuwabara, H. Inada, T. Wakimoto, H. Nakada, Y. Yonemoto, S. Kawami, and K. Imai., Appl. Phys. Lett. 65, 807 (1994)
26.C. Adachi, K. Nagai, and N. Tamoto, Appl. Phys. Lett. 68, 2679 (1996).
27.C. C. Wu, C. I. Wu, J. C. Sturm, and A. Kahn, Appl. Phys. Lett. 70, 1348 (1997).
28.S. K. So, W. K. Choi, C. H. Cheng, L. M. Leung, and C. F. Kwong, Appl. Phys. A: Mater. Sci. Process. 68, 447 (1999).
29.I M. Chan, W. C. Cheng, and F. C. Hong, Appl. Phys. Lett. 80, 13 (2002).
30.S. F. J. Appleyard, and M. R. Willis, Opt. Mater. 9, 120 (1998).
31.李玉華，”透明導電膜及其應用”，科儀新知，第十二卷第一期，(1990)94~102.
32.S. M. Tadayyon, K. Griffiths, P. R. Norton, C. Tripp, Z. Popovic, J. Vac. Sci. Technol. A17(1999) 1773.
33.K. L. Chopra, S. Major and D. K. Pandya, Thin Solid Films，102(1983)1~46.
34.蔡瑛修；”以感應式偶合電漿輔助磁控濺鍍法於低溫成長ITO膜”，國立成功大學化工所碩士論文 (2000).
35.楊明輝，工業材料雜誌，第179期，p.134.
36.H. Kawazoe, M. Yasukawa, H. Hyodo, M. Kurita, H. Yanagi, H. Hosono, Nature 389 (1997) 939.
37.T.L. Yang, D.H. Zhang, J. Ma, H.L. Ma, Y. Chen, Thin Solid Films,326,60(1998)
38.M.H. Francombe, S.V. Krishnaseamy, J. Vac. Sci. Technol. A, 8, 1382(1990)
39.B. Sang, A. Yamada, M. Konagai, Jpn. J. Appl. Phys., 37, L206(1998)
40.G. F. Neumark, Phys. Rev. Lett. 62, 1800 (1989).
41.T. Minami et al., Jpn. J. Appl. Phys. 24, L781 (1985).
42.S. B. Zhang, S.-H. Wei, and A. Zunger, J. Appl. Phys. 83, 3192 (1998).
43.D. J. Chadi, Phys. Rev. Lett. 72, 534 (1994).
44.S. B. Zhang, S.-H. Wei, and A. Zunger, Phys. Rev. Lett. 84, 1232 (2000).
45.T. Minami et al., Jpn. J. Appl. Phys. 24, L781 (1985); ibid. 25, L776 (1986).
46.J. Hu and R. G. Gordon, Sol. Cells 30, 437 (1991).
47.Y. Morinaga, K. Sakuragi, N. Fujimura, T. Ito, J. Crystal Growth 174 (1997) 691.
48.M. Hiramatsu, K. Imaeda, N. Horio, M. Nawata, J. Vac. Sci. Technol. A 16 (2) (1998) 669.
49.A. Kobayashi, O. F. Sankey, and J. D. Dow, Phys. Rev. B 28, 946 (1983).
50.Y. Sato and S. Sato, Thin Solid Films 281–282, 445 (1996).
51.K. Minegishi et al., Jpn. J. Appl. Phys. 36, L1453 (1997).
52.T. Yamamoto, H. Katayama-Yoshida, Physica. B, 302-303, 155(2001)
53.M. Joseph, H. Tabata, T. Kawai, Jpn. J. Appl. Phys. 38 (1999) L1205.
54.Y.R. Ryu, S. Zhu, D.C. Look, J.M. Wrobel, H.M. Jeong and H.W. White, J. Crystal Growth, 216, 330(2000)
55.D.C. Look, D.C. Reynolds, C.W. Litton, R.L. Jones, D.B. Eason and G. Cantwell, Appl. Phys. Lett., 81, 1830(2002)
56.X.-Li. Guo, H. Tabata and T. Kawai, Optical Materials, 19, 229(2002)
57.Y. Yan and S.B. Zhang, Phys. Rev. Lett., 86, 5723(2001)
58.I. D. Parker, J. Appl. Phys. 75, 1656(1994).
59.L.-B Lin, S. A. Jenekhe, R. H. Young, and P. M. Borsenberger, Appl. Phys. Lett., 70, 2052 (1997)
60.D. Z. Garbuzov, V. Bulović, P. E. Burrows, and P. E. Forest, Chem. Phys. Lett., 249, 433 (1996)
61.I-Min Chan, Tsung-Yi Hsu, and Franklin C. Hong, Appl. Phys. Lett., 81, 1899 (2002).
62.W. Hu, K. Manabe, T. Furukawa, and M. Matsumura, Appl. Phys. Lett.,80, 2640 (2002).
63.W. Hu, and M. Matsumura, Appl. Phys. Lett.81, 806 (2002)
64.Junji Kido, and Yasuhiro Lizumi, Appl. Phys. Lett.,73, 2721 (1998)
65.J. Huang, M. Pfeiffer, A. Werner, J. Blochwitz, K. Leo and S. Liu, Appl. Phys. Lett.,80, 139(2002)
66.Chris G. Van de Walle and J. Neugebauer, Nature, 423, 626(2003)
67.E.-C. Lee, Y.-S. Kim, Y.-G. Jin, K.J. Chang, Phys. B, 308-310, 912(2001).
68.B.-H. Cheong, C.H. Park, K.J. Chang, Phys. Rev. B 51, 10610(1995).
69.T. Suji and M. Hirohashi, Appl. Surf. Sci. 157, 47(2000)
70.Y. Kurosaka, N. Tada, Y. Ohmori, and K. Yoshino, Synth. Met. 102, 1101(1999).
71.Z. B. Deng, X. M. Ding, S. T. Lee, and W. A. Gambling, Appl. Phys. Lett. 74, 2227(1999).