藍光與白光有機電激發光元件：以高分子摻雜系統當發光層之研究

Studies of blue and white organic electroluminescent devices using the polymer/dopant systems as light-emitting layer

吳紹銘

高分子摻雜系統 ； 藍光與白光 ； 有機發光二極體 ； organic light-emitting diode ； blue and white light ； polymer-dopant system

成功大學光電科學與工程研究所學位論文

2006年

碩士

鄭弘隆

繁體中文

本研究以高分子與小分子混合的系統，採取旋轉塗佈的加工方式，製作藍光及白光有機發光二極體。小分子材料使用：藍光4,4’-bis(2,2-diphenylvinyl)-biphenyl (DPVBi)當發光層材料，tris(8-hydroxyquinoline)aluminum (Alq3)當電子傳輸層，2,9-Dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP)當電洞阻擋層。高分子材料使用：poly(9-vinylcarbazole) (PVK)當基體材料，polyfluorene綠光(PF-G)與polyfluorene紅光(PF-R)當發光層材料，poly(3,4-ethylenedioxythiophene):poly-(styrenesulfonate) (PEDOT:PSS)當電洞注入層；分別以Indium-tin oxide (ITO)與Ca/Al金屬當電洞與電子注入電極，製作元件結構為ITO/PEDOT:PSS/發光層/BCP/Alq3/Ca/Al的有機發光二極體，利用改變發光層材料與混合質量比例，分別製作藍光及白光元件。 　　第一部份，首先利用PVK與DPVBi依照質量比例混合當發光層製作藍光元件，使用吸收光譜、光激發光光譜、光致激發光譜與電激發光譜研究相關的光物理機制與能量轉移現象，進而探討元件的光電特性。本研究成功地製作出元件結構為ITO/PEDOT:PSS/PVK:DPVBi/BCP/Alq3/Ca/Al的藍光有機發光二極體，在9 V的驅動電壓下，亮度為1578 cd/m2，在153 mA/cm2的驅動電流下，發光效率為1.02 cd/A，Commission Internationale d’Eclairage (CIE)座標為(0.159 , 0.210)。此外，本研究發現PVK與DPVBi之間會有能量轉移現象，PVK會將能量轉移給DPVBi，增加DPVBi發光效率，且DPVBi有三個主要的振動放射峰。 　　第二部份，利用PVK、DPVBi、PF-G及PF-R依照質量比例混合當發光層製作白光元件，使用光激發光光譜、光致激發光譜與電激發光譜研究相關的光物理機制與能量轉移現象，進而探討元件的光電特性。本研究成功地製作出元件結構為ITO/PEDOT:PSS/PVK:DPVBi:PF-G:PF-R/BCP/Alq3/Ca/Al的白光有機發光二極體，在9 V的驅動電壓下，亮度為1390 cd/m2，在11.9 mA/cm2的驅動電流下，發光效率為0.347 cd/A，CIE座標為(0.302 , 0.335)。此外，本研究發現白光元件的光激發光光譜與電激發光光譜差異甚大，歸因於光激發光過程與電激發光過程中，發光材料間的能量轉移效率與作用力範圍不同。

In this study, blue and white organic electroluminescent diodes using polymer-dopant systems as emitting layer were fabricated. The emitting layer was produced via spin-coating process. Small-molecule materials that were used included: blue-emitting 4,4’-bis(2,2-diphenylvinyl)biphenyl (DPVBi) as a light-emitting layer material, tris(8-hydroxyquinoline)aluminum (Alq3) as an electron transport layer, and 2,9-Dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP) as a hole blocking layer. In addition to the small-molecule materials, the following polymer materials were used: poly(9-vinylcarbazole) (PVK) as a matrix material, polyfluorene green-emitting (PF-G) and polyfluorene red-emitting (PF-R) as light-emitting layer materials, and poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) as a hole injection layer. Indium-tin oxide (ITO) and Ca/Al were used as hole and electron injection electrodes accordingly. The device structure was comprised of ITO/PEDOT:PSS/light-emitting layer/BCP/Alq3/Ca/Al. Blue and white light-emitting devices were fabricated by changing light-emitting layer materials and altering proportion of their blending mass. 　In the first part, the blue light-emitting device was fabricated by blending PVK and DPVBi according to proportion of mass as specified for a light-emitting layer. Process relevant photophysical mechanisms and energy transfer phenomena were studied using absorption spectra, photoluminescence (PL) spectra, photoluminescent excitation (PLE) spectra, and electroluminescence (EL) spectra. Next, electro-optical characteristics of the device were studied. We have successfully fabricated the blue organic electroluminescent diode with the following structure: ITO/PEDOT:PSS/PVK:DPVBi/BCP/Alq3/Ca/Al. Fabricated blue organic electroluminescent diode has a brightness of 1578 cd/m2 at voltage of 9 V, luminance efficiency of 1.02 cd/A with applied current of 153 mA/cm2, and Commission Internationale d’Eclairage (CIE) coordinates (0.159 , 0.210). Moreover, we have learned that there was energy transfer phenomenon between PVK and DPVBi. PVK would transfer energy to DPVBi to enhance luminance efficiency of DPVBi, and DPVBi could exhibit three main vibronic peaks. 　In part two, the white light-emitting device was fabricated by blending PVK, DPVBi, PF-G, and PF-R in accordance with the proportion of mass of a light-emitting layer. Relevant photophysical mechanisms and energy transfer phenomena were studied by PL spectra, PLE spectra, and EL spectra. Additionally, electro-optical characteristics of the device were studied. We have successfully fabricated the white organic electroluminescent diode with the following structure: ITO/PEDOT:PSS/PVK:DPVBi:PF-G:PF-R/BCP/Alq3/Ca/Al. The white organic electroluminescent diode has a brightness of 1390 cd/m2 at voltage of 9 V, luminance efficiency of 0.347 cd/A at applied current of 11.9 mA/cm2, and CIE coordinates (0.302 , 0.335). Furthermore, we found that PL spectra and EL spectra of the white light-emitting device were very different because there may exist extraordinary energy transfer between used light-emitting materials.

1. [1] M. Pope, H. P. Kallmann, and P. Magnante, “Electroluminescence in Organic
   連結：
2. [2] C. W. Tang, and S. A. VanSlyke, “Organic Electroluminescent Diodes”,
   連結：
3. 　Appl. Phys. Lett., vol. 51, pp. 913－915, 1987.
   連結：
4. 　materials for organic light-emitting displays”, Proc. of SPIE, vol. 3797,
   連結：
5. 　pp. 120－128, 1999.
   連結：
6. 　organic light-emitting displays by solution processing”, Nature, vol.
   連結：
7. 　for full colour displays with organic light emitting diodes”,
   連結：
8. 　Nanotechnology, vol. 17, pp. 2246－2249, 2006.
   連結：
9. 　technology: materials, devices and display technologies”, Polym. Int.,
   連結：
10. 　Phosphorescent Polymer Light-Emitting Devices”, IEEE J. Sel. Top. Quantum
    連結：
11. 　efficiency white OLEDs based on small molecules”, Proc. of SPIE, vol.
    連結：
12. 　　“Characterization of white emitting copolymers for PLED-displays”, Proc.
    連結：
13. 　　K. Shim, “The Fabrication and Characterization of Single-Component
    連結：
14. [13] N. H. Lee, M. J. Lee, J. H. Song, C. Lee, D. H. Hwang, “Efficient white
    連結：
15. 　　organic electroluminescent devices consisting of blue- and red-emitting
    連結：
16. 　　layers”, Mater. Sci. Eng. C, vol. 24, pp. 233－235, 2004.
    連結：
17. [14] Y. S. Wu, S. W. Hwang, H. H. Chen, M. T. Lee, W. J. Shen, C. H. Chen,
    連結：
18. 　　“Efficient white organic light emitting devices with dual emitting
    連結：
19. 　　layers”, Thin Solid Films, vol. 488, pp. 265－269, 2005.
    連結：
20. 　　phosphorescent organic light-emitting devices with greenish-blue and red-
    連結：
21. 　　Exciton Diffusion in Multilayer White Phosphorescent Organic Light
    連結：
22. [17] C. H. Kim, and J. Shinar, “Bright small molecular white organic light-
    連結：
23. 　　Electrophosphorescent White-Light-Emitting Device with a Triple Doped
    連結：
24. [20] J. H. Jou, Y. S. Chiu, R. Y. Wang, H. C. Hu, C. P. Wang, H. W. Lin,
    連結：
25. 　　with an effective exciton-confining device architecture”, Org.
    連結：
26. [21] J. H. Jou, Y. S. Chiu, C. P. Wang, R. Y. Wang, and H. C. Hu, “Efficient,
    連結：
27. 　　color-stable fluorescent white organic light-emitting diodes with single
    連結：
28. 　　source”, Appl. Phys. Lett., vol. 88, 193501, 2006.
    連結：
29. 　　117, 2006.
    連結：
30. [23] J. H. Park, T. W. Lee, Y. C. Kim, O. O. Park, and J. K. Kim, “White
    連結：
31. 　　polymer light-emitting devices from ternary-polymer blend with
    連結：
32. 　　“White light emitting diodes using polymer blends”, Opt. Mater., vol.
    連結：
33. 　　21, pp. 205－210, 2002.
    連結：
34. [25] D. H. Hwang, M. J. Park, and C. Lee, “White LEDs using conjugated
    連結：
35. [26] J. H. Kim, P. Herguth, M. S. Kang, A. K. Y. Jen, Y. H. Tseng, and C. F.
    連結：
36. 　　Shu, “Bright white light electroluminescent devices based on a dye-
    連結：
37. 　　Electrophosphorescence from Polyfluorene-Based Light-Emitting Diodes:
    連結：
38. 　　“White-Light-Emitting Diodes Based on Iridium Complexes via Efficient
    連結：
39. 　　pp. 611－617, 2006.
    連結：
40. 　　printing of doped polymers for organic light emitting devices”, Appl.
    連結：
41. 　　Phys. Lett., vol. 72, pp. 519－521, 1998.
    連結：
42. 　　Baynes, “Recent developments in materials and processes for ink jet
    連結：
43. 　　printing high resolution polymer OLED displays”, Proc. of SPIE, vol.
    連結：
44. 　　“White Organic Electroluminescent Devices Fabricated Using Ink-Jet
    連結：
45. 　　Printing Method”, Jpn. J. Appl. Phys., vol. 43, pp. 7395－7398, 2004.
    連結：
46. 　　Printing in the Fabrication of Organic Light-Emitting Devices”, Adv.
    連結：
47. 　　Light-Emitting Devices Patterned by Screen-Printing”, Jpn. J. Appl.
    連結：
48. 　　Conjugated Polymers－Seeing Polymers in a New Light”, Angew. Chem. Int.
    連結：
49. 　　and energy transfer in organic light emitting diodes”, Phys. Stat. Sol.
    連結：
50. 　　Silsesquioxanes”, Jpn. J. Appl. Phys., vol. 45, pp. 550－554, 2006.
    連結：
51. 　　Polyfluorene-Based Polymer Light-Emitting Diodes”, Adv. Funct. Mater.,
    連結：
52. 　　Luminance of Blue Light-Emitting Polymers by Blending with Hole-
    連結：
53. 　　Transporting Materials”, Adv. Mater., vol. 15, pp. 1254－1258, 2003.
    連結：
54. 　　Efficient Blue Electroluminescence from Poly(phenylene ethynylene) via
    連結：
55. [41] J. H. Park, T. H. Kim, J. W. Yu, J. K. Kim, Y. C. Kim, and O. O. Park,
    連結：
56. 　　“Enhanced color purity and stability from polymer-nanoporous silica
    連結：
57. 　　“Confinement of triplet energy on phosphorescent molecules for highly-
    連結：
58. 　　Fluorescent OLED Materials and Devices”, IEEE/OSA J. Display Technol.,
    連結：
59. 　　organic light-emitting diodes with doped transport layers”, Synth. Met.,
    連結：
60. 　　7,8,10-triphenylfluoranthene-doped blue organic light-emitting diodes for
    連結：
61. 　　display application”, Appl. Phys. Lett., vol. 88, 093512, 2006.
    連結：
62. 　　and stable blue light-emitting diodes based on an anthracene derivative
    連結：
63. 　　White Organic Light-Emitting Devices Prepared on Flexible Plastic
    連結：
64. [49] F. I. Wu, C. F. Shu, T. T. Wang, E. W. G. Diau, C. H. Chien, C. H. Chuen,
    連結：
65. 　　and B. Geffroy, “Blue and white organic light emitting diodes based on a
    連結：
66. 　　Thompson, “Efficient Organic Electroluminescent Devices Using Single-
    連結：
67. 　　Abilities”, IEEE Trans. Electron Devices, vol. 44, pp. 1269－1281, 1997.
    連結：
68. 　　Bryce, “White polymeric light-emitting diode based on a fluorene
    連結：
69. 　Crystals”, J. Chem. Phys., vol. 38, pp. 2042－2043, 1963.
70. [3] J. H. Burroughes, D. D. C. Bradley, A. R. Brown, R. N. Marks, K. Mackay,
71. 　R. H. Friend, P. L. Burns, and A. B. Holmes, “Light-Emitting Diodes Based
72. 　on Conjugated Polymers”, Nature, vol. 347, pp. 539－541, 1990.
73. [4] S. I. Tamura, Y. Kijima, N. Asai, M. Ichimura, and T. Ishibashi, “RGB
74. [5] C. D. Müller, A. Falcou, N. Reckefuss, M. Rojahn, V. Wiederhirn, P.
75. 　Rudati, H. Frohne, O. Nuyken, H. Becker, and K. Meerholz, “Multi-colour
76. 　421, pp. 829－833, 2003.
77. [6] J. H. Choi, K. H. Kim, S. J. Choi, and H. H. Lee, “Whole device printing
78. [7] B. Geffroy, P. L. Roy, and C. Prat, “Organic light-emitting diode (OLED)
79. 　vol. 55, pp. 572－582, 2006.
80. [8] M. Suzuki, T. Hatakeyama, S. Tokito, and F. Sato, “High-Efficiency White
81. 　Electron., vol. 10, pp. 115－120, 2004.
82. [9] T. K. Hatwar, J. P. Spindler, M. L. Ricks, R. H. Young, Y. Hamada, N.
83. 　Saito, K. Mameno, R. Nishikawa, H. Takahashi, and G. Rajeswaran, “High-
84. 　5214, pp. 233－240, 2004.
85. [10] D. Buchhauser, M. Scheffel, W. Rogler, C. Tschamber, K. Heuser, A. Hunze,
86. 　　G. Gieres, D. Henseler, W. Jakowetz, K. Diekmann, A. Winnacker, H.
87. 　　Becker, A. Büsing, A. Falcou, L. Rau, S. Vögele, S. Göttling,
88. 　　of SPIE, vol. 5519, pp. 70－81, 2004.
89. [11] B. W. D’Andrade, and S. R. Forrest, “White Organic Light-Emitting
90. 　　Devices for Solid-State Lighting”, Adv. Mater., vol. 16, pp. 1585－1595,
91. 　　2004.
92. [12] S. K. Lee, D. H. Hwang, B. J. Jung, N. S. Cho, J. Lee, J. D. Lee, and H.
93. 　　Polymeric White-Light-Emitting Diodes”, Adv. Funct. Mater., vol. 15, pp.
94. 　　1647－1655, 2005.
95. [15] S. Tokito, T. Iijima, T. Tsuzuki, and F. Sato, “High-efficiency white
96. 　　emitting layers”, Appl. Phys. Lett., vol. 83, pp. 2459－2461, 2003.
97. [16] B. W. D’Andrade, M. E. Thompson, and S. R. Forrest, “Controlling
98. 　　Emitting Devices”, Adv. Mater., vol. 14, pp. 147－151, 2002.
99. 　　emitting devices with two emission zones”, Appl. Phys. Lett., vol. 80,
100. 　　pp. 2201－2203, 2002.
101. [18] C. H. Chuen, and Y. T. Tao, “Highly-bright white organic light-emitting
102. 　　diodes based on a single emission layer”, Appl. Phys. Lett., vol. 81,
103. 　　pp. 4499－4501, 2002.
104. [19] B. W. D’Andrade, R. J. Holmes, and S. R. Forrest, “Efficient Organic
105. 　　Emissive Layer”, Adv. Mater., vol. 16, pp. 624－628, 2004.
106. 　　“Efficient, color-stable fluorescent white organic light-emitting diodes
107. 　　Electron., vol. 7, pp. 8－15, 2006.
108. 　　emission layer by vapor deposition from solvent premixed deposition
109. [22] J. Huang, G. Li, E. Wu, Q. Xu, and Y. Yang, “Achieving High-Efficiency
110. 　　Polymer White-Light-Emitting Devices”, Adv. Mater., vol. 18, pp. 114－
111. 　　concentration gradient”, Chem. Phys. Lett., vol. 403, pp. 293－297, 2005.
112. [24] J. I. Lee, H. Y. Chu, S. H. Kim, L. M. Do, T. Zyung, and D. H. Hwang,
113. 　　polymer blends”, Synth. Met., vol. 152, pp. 205－208, 2005.
114. 　　dispersed polyfluorene derivative”, Appl. Phys. Lett., vol. 85, pp.
115. 　　1116－1118, 2004.
116. [27] J. Kido, H. Shionoya, and K. Nagai, “Single-layer white light-emitting
117. 　　organic electroluminescent devices based on dye-dispersed poly(N-
118. 　　vinylcarbazole)”, Appl. Phys. Lett., vol. 67, pp. 2281－2283, 1995.
119. [28] X. Gong, D. Moses, A. J. Heeger, and S. Xiao, “White Light
120. 　　Utilization of Fluorenone Defects”, J. Phys. Chem. B, vol. 108, pp.
121. 　　8601－8605, 2004.
122. [29] T. H. Kim, H. K. Lee, O. O. Park, B. D. Chin, S. H. Lee, and J. K. Kim,
123. 　　Energy Transfer from a Conjugated Polymer”, Adv. Funct. Mater., vol. 16,
124. [30] T. R. Hebner, C. C. Wu, D. Marcy, M. H. Lu, and J. C. Sturm, “Ink-jet
125. [31] J. C. Carter, A. Wehrum, M. C. Dowling, M. C. Martinez, and N. D. B.
126. 　　4800, pp. 34－46, 2003.
127. [32] R. Satoh, S. Naka, M. Shibata, H. Okada, H. Onnagawa, and T. Miyabayashi,
128. [33] D. A. Pardo, G. E. Jabbour, and N. Peyghambarian, “Application of Screen
129. 　　Mater., vol. 12, pp. 1249－1252, 2000.
130. [34] K. Mori, T. Ning, M. Ichckawa, T. Koyama, and Y. Taniguchi, “Organic
131. 　　Phys., vol. 39, pp. 942－944, 2000.
132. [35] A. Kraft, A. C. Grimsdale, and A. B. Holmes, “Electroluminescent
133. 　　Ed., vol. 37, pp. 402－428, 1998.
134. [36] M. Baldo, and M. Segal, “Phosphorescence as a probe of exciton formation
135. 　　(a), vol. 201, pp. 1205－1214, 2004.
136. [37] L. Fenenko, Y. Nakanishi, S. Tokito, and A. Konno, “Electronic
137. 　　Characterization of New Bright-Blue-Light-Emitting Poly(9,9-
138. 　　dioctylfluorenyl-2,7-diyl)-End Capped With Polyhedral Oligomeric
139. [38] T. V. Woudenbergh, J. Wildeman, P. W. M. Blom, J. J. A. M. Bastiaansen,
140. 　　and B. M. W. L. Voss, “Electron-Enhanced Hole Injection in Blue
141. 　　vol. 14, pp. 677－683, 2004.
142. [39] M. C. Suh, B. D. Chin, M. H. Kim, T. M. Kang, and S. T. Lee, “Enhanced
143. [40] C. A. Breen, J. R. Tischler, V. Bulović, and T. M. Swager, “Highly
144. 　　Energy Transfer from a Hole-Transport Matrix”, Adv. Mater., vol. 17, pp.
145. 　　1981－1985, 2005.
146. 　　nanocomposite blue light-emitting diodes”, Synth. Met., vol. 154, pp.
147. 　　145－148, 2005.
148. [42] S. Tokito, T. Iijima, Y. Suzuri, H. Kita, T. Tsuzuki, and F. Sato,
149. 　　efficient organic blue-light-emitting devices”, Appl. Phys. Lett., vol.
150. 　　83, pp. 569－571, 2003.
151. [43] S. W. Wen, M. T. Lee, and C. H. Chen, “Recent Development of Blue
152. 　　vol. 1, pp. 90－99, 2005.
153. [44] D. Gebeyehu, K. Walzer, G. He, M. Pfeiffer, K. Leo, J. Brandt, A.
154. 　　Gerhard, P. Stößel, and H. Vestweber, “Highly efficient deep-blue
155. 　　vol. 148, pp. 205－211, 2005.
156. [45] A. Fischer, S. Chénais, S. Forget, M. C. Castex, D. Adès, A. Siove, C.
157. 　　Denis, P. Maisse, and B. Geffroy, “Highly efficient multilayer organic
158. 　　pure blue light emitting diodes with substituted carbazoles compounds in
159. 　　the emitting layer”, J. Phys. D: Appl. Phys., vol. 39, pp. 917－922,
160. 　　2006.
161. [46] R. J. Tseng, R. C. Chiechi, F. Wudl, and Y. Yang, “Highly efficient
162. [47] Y. H. Niu, B. Chen, T. D. Kim, M. S. Liu, and A. K. Y. Jen, “Efficient
163. 　　doped poly(N-vinylcarbazole)”, Appl. Phys. Lett., vol. 85, pp. 5433－
164. 　　5435, 2004.
165. [48] A. Mikami, T. Koshiyama, and T. Tsubokawa, “High-Efficiency Color and
166. 　　Substrates”, Jpn. J. Appl. Phys., vol. 44, pp. 608－612, 2005.
167. 　　and Y. T. Tao, “Bis(2,2-diphenylvinyl)spirobifluorene: An efficient and
168. 　　stable blue emitter for electroluminescence applications”, Synth. Met.,
169. 　　vol. 151, pp. 285－292, 2005.
170. [50] N. Lemaître, J. Lavigne, P. Raimond, T. Maindron, C. Denis, P. Maisse,
171. 　　doped DPVBi emitting layer”, Proc. of SPIE, vol. 5937, 593723, 2005.
172. [51] C. C. Wu, J. C. Sturm, R. A. Register, J. Tian, E. P. Dana, and M. E.
173. 　　Layer Doped Polymer Thin Films with Bipolar Carrier Transport
174. [52] H. A. A. Attar, A. P. Monkman, M. Tavasli, S. Bettington, and M. R.
175. 　　polymer/Ir complex blend system”, Appl. Phys. Lett., vol. 86, 121101,
176. 　　2005.