最近的研究顯示高分子發光二極體(PLEDs)本身具有良好發光特性，其發光機制是利用電激發光，即是利用電子電洞分別從陰極與陽極注入，傳輸到發光層再結合而發光。然而大部分高分子材料的電洞傳輸速率都比電子還要快，會造成發光層載子不平衡，因此影響發光效率。所以降低電洞的傳輸速率則是讓高分子發光二極體電流效率上升的有效方法之一。
本研究成功利用Suzuki Coupling Reaction分別合成出主鏈含1,3,4-噁二唑基團的高分子(P1)與1,2,4-三氮唑基團的高分子(P2)，並將其應用於高分子發光二極體的電洞緩衝層(Hole-Buffer Layer: HBL)，以核磁共振光譜(1H-NMR)、元素分析儀(EA)、紅外線光譜儀(FTIR)鑑定其結構，並分析其熱性質、光學性質、電化學性質、膜態及發光二極體的電激發光特性。
P1與P2具有高的熱裂解溫度(Td >350 oC)；P1及P2的薄膜態吸收光譜皆有兩個吸收峰，而薄膜態發光波長分別在562 nm及544 nm；從循環伏安法量測出P1與P2的最低未占有分子軌域(LUMO)及最高占有分子軌域(HOMO)能階分別為-5.37/-2.54 eV與-5.33/-2.31 eV。
將P1與P2利用旋轉塗佈的方式製備電洞緩衝層(HBL)應用於電激發光元件(ITO/PEDOT:PSS/HBL/SY-PPV/LiF/Al )，在無電洞緩衝層的元件其最大亮度為12,352 cd/m2，最大電流效率為2.30 cd/A；加入P1作為電洞緩衝層元件，最大亮度提高至15,503 cd/m2，最大電流效率為4.91 cd/A；加入P2作為電洞緩衝層元件，最大亮度提高至21,227 cd/m2，最大電流效率為8.08 cd/A。
研究結果顯示，以P2為電洞緩衝層具有較佳的元件性能，原因除了其具有較佳的電洞緩衝能力外，還具有電子阻擋能力，使到達發光層的載子更加平衡，大幅度提升元件的表現。但是由亮度及電流效率觀之，P1與P2都是具有實用潛力之新穎電洞緩衝材料。

In recent years, polymer light-emitting diodes (PLEDs) have been attention for its self-emissive ability, flexibility, wide view angle and high efficiency. Charge balance is an important factor to enhance device efficiency. In most organic materials, hole mobility is always higher than electron mobility, so using a material which can reduce hole mobility to increase PLEDs efficiency. In this study, we successfully synthesized two new polyimines (P1 and P2) by Suzuki-coupling reaction. P1 and P2 composed 1,3,4-oxadiazolyl and 1,2,4-triazolyl groups, respectively were applied for hole buffer layer (HBL) by solution process. P1 and P2 possess excellent thermal stability (Td > 350 oC) because of rigid structure. In cyclic voltammetry measurement, HOMO/LUMO energy levels of P1 and P2 were -5.37/-2.54 and -5.33/-2.31 eV, respectively. Multilayer PLED devices were successfully fabricated [ITO/PEDOT:PSS/HBL/SY-PPV/LiF/Al], and P1 or P2 as HBL was deposited by spin-coating process. The maximum luminance and maximum current efficiency of P2-based device were 20,058 cd/m2 and 8.08 cd/A, respectively, better than P1-based one (15,503 cd/m2, 4.91 cd/A) and the device without HBL (12,352 cd/m2, 2.3 cd/A). Furthermore, both P1 and P2 are efficient hole buffer materials.

[1] M. Pope, H.P. Kallmann, and P. Magnante, Electroluminescence in organic crystals. The Journal of Chemical Physics, 1963. 38(8): p. 2042-2043.
[2] C.W. Tang and S.A. VanSlyke, Organic electroluminescent diodes. Applied physics letters, 1987. 51(12): p. 913-915.
[3] J. Burroughes, D. Bradley, A. Brown, R. Marks, K. Mackay, R. Friend, P. Burns, and A. Holmes, Light-emitting diodes based on conjugated polymers. nature, 1990. 347(6293): p. 539-541.
[4] 段啟聖, 化工資訊雜誌與商情, 2005. 第26期: p. 40.
[5] 郭昭輝, 塑膠資訊雜誌, 2002.
[6] B. Valeur and M.N. Berberan-Santos, Molecular fluorescence: principles and applications. 2012: John Wiley & Sons.
[7] M. Lax, The Franck‐Condon Principle and Its Application to Crystals. The Journal of Chemical Physics, 1952. 20(11): p. 1752-1760.
[8] W. Yip and D.H. Levy, Excimer/exciplex formation in van der Waals dimers of aromatic molecules. The Journal of Physical Chemistry, 1996. 100(28): p. 11539-11545.
[9] S. Beck, A. Hallam, and A. North, Excimer and charge transfer complex trapping of excitons in carbazole containing polymers. Polymer, 1979. 20(10): p. 1177-1179.
[10] J. Guillet, Polymer photophysics and photochemistry. 1985.
[11] V. May and O. Kühn, Charge and energy transfer dynamics in molecular systems, 2nd. Charge and Energy Transfer Dynamics in Molecular Systems, 2nd, Revised and Enlarged Edition, by Volkhard May, Oliver Kühn, pp. 490. ISBN 3-527-40396-5. Wiley-VCH, February 2004., 2004: p. 490.
[12] L.T. Corporation, Fluorescence Resonance Energy Transfer (FRET)-Note 1.2.
[13] K. Walzer, B. Maennig, M. Pfeiffer, and K. Leo, Highly efficient organic devices based on electrically doped transport layers. Chemical reviews, 2007. 107(4): p. 1233-1271.
[14] 黃孝文 and 陳雲, 化工資訊月刊, 2001. 第3期: p. 8.
[15] 葉昆明 and 陳雲, 科學發展, 2005. 第385期: p. 58.
[16] 陳信宏 and 陳雲, 中工高雄會刊, 2006. 第3期: p. 72.
[17] M. Baldo, M. Thompson, and S. Forrest, High-efficiency fluorescent organic light-emitting devices using a phosphorescent sensitizer. Nature, 2000. 403(6771): p. 750-753.
[18] G. Malliaras, J. Salem, P. Brock, and C. Scott, Electrical characteristics and efficiency of single-layer organic light-emitting diodes. Physical Review B, 1998. 58(20): p. R13411.
[19] C.C. Wu, J.C. Sturm, R.A. Register, J. Tian, E.P. Dana, and M. Tnompson, Efficient organic electroluminescent devices using single-layer doped polymer thin films with bipolar carrier transport abilities. IEEE Transactions on Electron Devices, 1997. 44(8): p. 1269-1281.
[20] 陳金鑫 and 黃孝文, 夢幻顯示器 OLED 材料與元件. 2012: 台灣:五南圖書出版社.
[21] J. Segura, The chemistry of electroluminescent organic materials. Acta Polymerica, 1998. 49(7): p. 319-344.
[22] B.S. Ong, Y. Wu, P. Liu, and S. Gardner, High-performance semiconducting polythiophenes for organic thin-film transistors. Journal of the American Chemical Society, 2004. 126(11): p. 3378-3379.
[23] K.M. Coakley and M.D. McGehee, Conjugated polymer photovoltaic cells. Chemistry of materials, 2004. 16(23): p. 4533-4542.
[24] J. Roncali, Conjugated poly (thiophenes): synthesis, functionalization, and applications. Chemical Reviews, 1992. 92(4): p. 711-738.
[25] M.C. Choi, Y. Kim, and C.-S. Ha, Polymers for flexible displays: From material selection to device applications. Progress in Polymer Science, 2008. 33(6): p. 581-630.
[26] A.J. Heeger, Semiconducting and metallic polymers: the fourth generation of polymeric materials. 2001, ACS Publications.
[27] G. Malliaras and J. Scott, The roles of injection and mobility in organic light emitting diodes. Journal of Applied Physics, 1998. 83(10): p. 5399-5403.
[28] R. Kepler, Charge carrier production and mobility in anthracene crystals. Physical Review, 1960. 119(4): p. 1226.
[29] E. Martin and J. Hirsch, Determination of carrier mobility in plastics by a time-of-flight method. Solid State Communications, 1969. 7(10): p. 783-786.
[30] G. Horowitz, Organic field-effect transistors. Advanced Materials, 1998. 10(5): p. 365-377.
[31] A. Babel and S.A. Jenekhe, High electron mobility in ladder polymer field-effect transistors. Journal of the American Chemical Society, 2003. 125(45): p. 13656-13657.
[32] X. Zhang and S.A. Jenekhe, Electroluminescence of multicomponent conjugated polymers. 1. Roles of polymer/polymer interfaces in emission enhancement and voltage-tunable multicolor emission in semiconducting polymer/polymer heterojunctions. Macromolecules, 2000. 33(6): p. 2069-2082.
[33] S.A. Jenekhe and S. Yi, Efficient photovoltaic cells from semiconducting polymer heterojunctions. Applied Physics Letters, 2000. 77(17): p. 2635-2637.
[34] J. Li, J. Liu, C. Gao, J. Zhang, and H. Sun, Influence of MWCNTs doping on the structure and properties of PEDOT: PSS films. International Journal of Photoenergy, 2009. 2009.
[35] D. Grozea, A. Turak, Y. Yuan, S. Han, Z. Lu, and W. Kim, Enhanced thermal stability in organic light-emitting diodes through nanocomposite buffer layers at the anode/organic interface. Journal of applied physics, 2007. 101(3): p. 033522.
[36] S. Tadayyon, H. Grandin, K. Griffiths, P. Norton, H. Aziz, and Z. Popovic, CuPc buffer layer role in OLED performance: a study of the interfacial band energies. Organic Electronics, 2004. 5(4): p. 157-166.
[37] E. Forsythe, M. Abkowitz, and Y. Gao, Tuning the carrier injection efficiency for organic light-emitting diodes. The Journal of Physical Chemistry B, 2000. 104(16): p. 3948-3952.
[38] V.I. Adamovich, S.R. Cordero, P.I. Djurovich, A. Tamayo, M.E. Thompson, B.W. D’Andrade, and S.R. Forrest, New charge-carrier blocking materials for high efficiency OLEDs. Organic electronics, 2003. 4(2): p. 77-87.
[39] W.-C. Lin, H.-W. Lin, E. Mondal, and K.-T. Wong, Efficient solution-processed green and white phosphorescence organic light-emitting diodes based on bipolar host materials. Organic Electronics, 2015. 17: p. 1-8.
[40] H. Gao, C. Qin, H. Zhang, S. Wu, Z.-M. Su, and Y. Wang, Theoretical characterization of a typical hole/exciton-blocking material bathocuproine and its analogues. The Journal of Physical Chemistry A, 2008. 112(38): p. 9097-9103.
[41] T.W. Lee, T. Noh, H.W. Shin, O. Kwon, J.J. Park, B.K. Choi, M.S. Kim, D.W. Shin, and Y.R. Kim, Characteristics of solution‐processed small‐molecule organic films and light‐emitting diodes compared with their vacuum‐deposited counterparts. Advanced Functional Materials, 2009. 19(10): p. 1625-1630.
[42] M. Wohlgenannt, K. Tandon, S. Mazumdar, S. Ramasesha, and Z. Vardeny, Formation cross-sections of singlet and triplet excitons in π-conjugated polymers. Nature, 2001. 409(6819): p. 494-497.
[43] F. Huang, H. Wu, and Y. Cao, Water/alcohol soluble conjugated polymers as highly efficient electron transporting/injection layer in optoelectronic devices. Chemical Society Reviews, 2010. 39(7): p. 2500-2521.
[44] W. Ma, P.K. Iyer, X. Gong, B. Liu, D. Moses, G.C. Bazan, and A.J. Heeger, Water/Methanol‐Soluble Conjugated Copolymer as an Electron‐Transport Layer in Polymer Light‐Emitting Diodes. Advanced Materials, 2005. 17(3): p. 274-277.
[45] C.L. Wu, C.Y. Lin, and Y. Chen, Fabrication of efficient polymer light-emitting diodes using water/alcohol soluble poly (vinyl alcohol) doped with alkali metal salts as electron-injection layer. Journal of materials science, 2016. 51(15): p. 7286-7299.
[46] Z. Gao, R. Huang, Y. Lin, Y. Zheng, Y. Liu, and B. Wei, Reduced turn-on voltage and improved efficiency with free interfacial energy barrier in organic light-emitting diodes. Synthetic Metals, 2015. 207: p. 26-30.
[47] Y.J. Cho, K.S. Yook, and J.Y. Lee, A universal host material for high external quantum efficiency close to 25% and long lifetime in green fluorescent and phosphorescent OLEDs. Advanced Materials, 2014. 26(24): p. 4050-4055.
[48] N. Miyaura and A. Suzuki, Stereoselective synthesis of arylated (E)-alkenes by the reaction of alk-1-enylboranes with aryl halides in the presence of palladium catalyst. Journal of the Chemical Society, Chemical Communications, 1979(19): p. 866-867.
[49] J.F. Rusling and S.L. Suib, Characterizing materials with cyclic voltammetry. Advanced Materials, 1994. 6(12): p. 922-930.
[50] 黃英碩, 掃描探針顯微術的原理及應用. 科儀新知, 2005(144): p. 7-17.
[51] 高豐生, 陳大潘, and 陳惠民, 利用原子力顯微鏡技術來研究蛋白質固定在晶片上的方向性. 國家奈米元件實驗室奈米通訊, 2010. 17(3): p. 2-6.
[52] B. Stegemann, H. Backhaus, H. Kloß, and E. Santner, Spherical AFM probes for adhesion force measurements on metal single crystals. Modern Research and Educational Topics in Microscopy, Series, 2007. 3: p. 820-827.
[53] 朱柏豪, 表面輪廓儀的用途. 國家奈米元件實驗室奈米通訊, 2015. 22(1): p. 31-33.
[54] K. Manabe, W. Hu, M. Matsumura, and H. Naito, Transport of carriers in organic light-emitting devices fabricated with ap-phenylenevinylene-derivative copolymer. Journal of applied physics, 2003. 94(3): p. 2024-2027.
[55] R. Steyrleuthner, S. Bange, and D. Neher, Reliable electron-only devices and electron transport in n-type polymers. Journal of Applied Physics, 2009. 105(6): p. 064509.
[56] M.F. Zaltariov, M. Cazacu, S. Shova, C.D. Varganici, L. Vacareanu, V. Musteata, and A. Airinei, A silicon-containing polyazomethine and derived metal complexes: synthesis, characterization, and evaluation of the properties. Designed Monomers and Polymers, 2014. 17(7): p. 668-683.
[57] M.F. Zaltariov, M. Cazacu, C. Racles, V. Musteata, A. Vlad, and A. Airinei, Metallopolymers based on a polyazomethine ligand containing rigid oxadiazole and flexible tetramethyldisiloxane units. Journal of Applied Polymer Science, 2015. 132(11).
[58] B.Y. Hsieh, K.M. Yeh, and Y. Chen, Synthesis of electroluminescent copoly (aryl ether) s containing alternate 1, 4‐distyrylbenzene derivatives and aromatic 1, 3, 4‐oxadiazole or 3, 3"‐terphenyldicarbonitrile segments. Journal of Polymer Science Part A: Polymer Chemistry, 2005. 43(21): p. 5009-5022.
[59] Y.R. Pu and Y. Chen, Solution-processable bipolar hosts based on triphenylamine and oxadiazole derivatives: synthesis and application in phosphorescent light-emitting diodes. Journal of Luminescence, 2016. 170: p. 127-135.
[60] J.M. Rathfon, Z.M. AL-Badri, R. Shunmugam, S.M. Berry, S. Pabba, R.S. Keynton, R.W. Cohn, and G.N. Tew, Fluorimetric Nerve Gas Sensing Based on Pyrene Imines Incorporated into Films and Sub‐Micrometer Fibers. Advanced Functional Materials, 2009. 19(5): p. 689-695.
[61] S.H. Chen and Y. Chen, Poly (p-phenylenevinylene) derivatives containing electron-transporting aromatic triazole or oxadiazole segments. Macromolecules, 2005. 38(1): p. 53-60.
[62] C.S. Wu, Y.S. Wu, and Y. Chen, Water-soluble 1, 2, 4-triazole with diethylene glycol monoethyl ether groups: synthesis, characterization and application as an electron injection layer for PLEDs. Physical Chemistry Chemical Physics, 2014. 16(19): p. 8927-8934.
[63] C.S. Wu and Y. Chen, Copolyfluorenes containing pendant bipolar carbazole and 1, 2, 4‐triazole groups: Synthesis, characterization, and optoelectronic applications. Journal of Polymer Science Part A: Polymer Chemistry, 2011. 49(18): p. 3928-3938.
[64] L.S. Pingree, B.A. MacLeod, and D.S. Ginger, The changing face of PEDOT: PSS films: Substrate, bias, and processing effects on vertical charge transport. The Journal of Physical Chemistry C, 2008. 112(21): p. 7922-7927.
[65] S.Y. Chou and Y. Chen, Hole‐buffer polymer composed of alternating p‐terphenyl and tetraethylene glycol ether moieties: Synthesis and application in polymer light‐emitting diodes. Journal of Polymer Science Part A: Polymer Chemistry, 2016. 54(6): p. 785-794.
[66] D.A. Mengistie, M.A. Lbrahem, P.C. Wang, and C.W. Chu, Highly conductive PEDOT: PSS treated with formic acid for ITO-free polymer solar cells. ACS applied materials & interfaces, 2014. 6(4): p. 2292-2299.