臺灣博碩士論文加值系統

本研究利用藍光磷光銥錯合物iridium(III) bis[(4,6-di-fluorophenyl)-pyridinato-N,C2''] (FIrpic)以及橘黃光磷光銥錯合物Iridium(III) bis (4-phenylthieno [3,2-c]pyridinato-N,C2′)acetylacetonate (PO-01)摻雜於小分子磷光主體N, N_-dicarbazolyl-3, 5-benzene (mCP)製作出白色磷光有機發光二極體(white PHOLED)，並使用電荷控制層的概念，提升白色磷光有機發光二極體之發光效率。
藍色磷光客體材料(FIrpic)之EL頻譜波峰位於472 nm，而橘黃色磷光材料(PO-01)之EL頻譜波峰位於560 nm，利用此雙發光層以及超薄的電荷控制層(mCP)結構可製作白色磷光有機發光二極體元件。首先，探討磷光客體材料之最佳摻雜濃度以及其結構上加入電荷控制層後載子的傳輸機制，進而研究雙發光層厚度比例對於元件特性的影響。
實驗結果顯示在客體材料最佳摻雜濃度以及電荷控制層最佳厚度條件下，成功製造出具有高色穩定性以及高效率之白色磷光有機發光二極體元件，元件結構為 ITO/m-MTDATA(40 nm)/α-NPB(30 nm)/mCP(10 nm)/mCP:FIrpic(23.2 nm, 10 wt%)/mCP(1 nm)/mCP:PO-01(5.8 nm, 2 wt%)/TPBi(40 nm)/LiF/Al，此元件最大發光效率為30.06 cd/A、最大亮度 17000 cd/m2、色度座標CIE(0.33, 0.41)，其CIE變化值僅為(±0.01, ±0.01)具高色穩定性。

In this paper, we dope blue phosphorescent iridium complexes iridium(III)bis[(4,6-di-fluorophenyl)-pyridinato-N,C2''] (FIrpic) and yellow phosphorescent iridium complexes Iridium(III) bis (4-phenylthieno [3,2-c]pyridinato-N,C2′)acetylacetonate (PO-01) into the small molecular phosphorescent host N, N_-dicarbazolyl-3, 5-benzene (mCP) to fabricate white phosphorescent organic light-emitting diodes (white PHOLEDs). Device current efficiency is enhanced by inserting a charge control layer (CCL) into the emitting layer.
The peaks of PHOLED electroluminescent (EL) spectrum locate at 472 nm (FIrpic) and 560 nm (PO-01). A high current efficiency white PHOLED has been fabricated by the use of FIrpic and Po-01 as the double emitting layer (EML), in which the mCP is used as the CCL inserted. The doping concentration of PO-01 is optimized and the carrier transport mechanism of CCL is discussed. Afterward, the thickness of each EML is modified to observe the luminous characteristics.
Experimental results reveal that we have successfully fabricated high efficiency and color stability white PHOLED by optimizing the doping concentration of PO-01 and the thickness of CCL. Optimized device structure is ITO/m-MTDATA(40 nm)/α-NPB(30 nm)/mCP(10 nm)/mCP:FIrpic(23.2 nm, 10 wt%)/mCP(1 nm)/mCP:PO-01(5.8 nm, 2 wt%)/TPBi(40 nm)/LiF/Al. The maximum current efficiency of 30.06 cd/A and luminance of 17000 cd/m2 have been achieved. Its CIE coordinates locate at (0.33, 0.41) and vary within (±0.01, ±0.01).

目錄
中文摘要 I
ABSTRACT II
致謝 IV
目錄 V
表目錄 VIII
圖目錄 IX
第一章 緒論 1
1-1 前言 1
1-2 有機發光二極體(OLED)之發展及產業現況 2
1-3 研究動機及目的 4
第二章 有機發光二極體理論及結構 10
2-1 有機發光二極體(OLED)之簡介 10
2-2 有機發光二極體之元件結構 12
2-3 有機發光二極體元件常用材料 14
2-3-1 陽極(Anode) 14
2-3-2 電洞注入材料(Hole Injection Material) 15
2-3-3 電洞傳輸材料(Hole Transporting Material) 16
2-3-4 發光層材料(Emissive Layer Material) 16
2-3-5 電子傳輸層材料(Electron Transporting Material) 18
2-3-6 電子注入層材料(Electron Injection Material) 19
2-3-7 陰極(Cathode) 19
2-4 有機發光二極體之電激發光理論 20
2-4-1 電激發光工作原理 20
2-4-2 螢光(Fluorescence)與磷光(Phosphorescence) 21
2-4-3 摻雜系統之能量轉移 23
2-5 白光有機發光二極體之實現方法 23
2-6 色轉換層實現白光放射的理論分析 25
2-7 真空熱蒸鍍原理 26
2-8 有機發光二極體之衰減機制 26
2-9 TTA (Triplet-Triplet Annilation) 28
第三章 實驗步驟和方法 38
3-1 玻璃基板 38
3-1-1 ITO玻璃基板 38
3-1-2 基板圖案呈現 39
3-1-3 ITO表面潔淨處理 40
3-2 實驗材料 40
3-2-1 有機材料 40
3-2-2 氧化物材料 41
3-2-3 金屬材料 41
3-3 材料膜厚之校正 41
3-4 使用設備及儀器介紹 42
3-5有機發光二極體製程 43
3-6 元件量測與薄膜分析 44
第四章 結果與討論 50
4-1 白色磷光有機發光二極體之設計概念 50
4-1-1 探討能量轉移機制 50
4-1-2 材料能階與PO-01在不同摻雜濃度對元件光電特影響 51
4-2使用電荷控制層提升元件發光效率 52
4-3白色磷光有機發光二極體製作 54
4-3-1 使用雙層藍光的發光層和一層橘黃光的發光層 54
4-3-2 將調變橘黃光發光層位置 55
4-4 調變發光層厚度比例改善元件光電特性 56
第五章 結論與展望 75
5-1 結論 75
5-2 展望 76
參考文獻 77

 
表目錄
表1-1 相同尺寸的LCD與OLED之特性比較。[ITRI工業技術研究院] 6
表2-1 OLED、PLED在材料特性上優缺點比較 30
表4-1(a). Device A1-A3之特性表格，(b). Device A之特性表格 58
表4-2 Device B之特性表格 59
表4-3 Device C之特性表格 59
表4-4 Device D之特性表格 59

 
圖目錄
圖1-1 WOLED與其他光源比較圖 7
圖1-2蒽（Anthrathcene）的晶體 7
圖1-3歐司朗公司白光OLED照明面板原型 8
圖1-4 歐司朗公司白光OLED照明面板原型 8
圖1-5 多層推疊實現白光放射之OLED結構圖 9
圖2-1 異質接面結構元件示意圖 31
圖2-2 1990年Adachi等人所發表的幽禁式(confinement)的三層結構 31
圖2-3 A.Mikami等人提出之UV-OLED結構與能階圖 32
圖2-4 2009年Yuan等人所發表的白光結構 32
圖2-5 2010年Giner-Casares等人所發表的白光結構 33
圖2-6 雙層OLED結構(a)以電子傳輸層發光(b)以電洞傳輸層發光 33
圖2-7 OLED不同結構圖 [取自夢幻顯示器 第39頁] 34
圖2-8小分子元件結構演進圖 34
圖2-9 有機發光二極體基本元件結構圖 35
圖2-10 分子能階簡圖 35
圖2-11 能量轉移機制 36
圖2-12 白光OLED元件結構 36
圖2-13 真空蒸鍍機之照片 37
圖3-1 黃光製程流程圖 46
圖3-2 實驗使用材料之分子結構圖 46
圖3-3 真空蒸鍍系統示意圖 47
圖3-4 玻璃切割機 47
圖3-5旋轉塗佈機台照片 48
圖3-6 封裝用點膠機 48
圖3-7 有機發光元件封裝示意圖 49
圖3-8 量測設備配置示意圖 49
圖4-1 Device A 元件結構圖 60
圖4-2 磷光元件發光層之主客體材料PL與吸收光譜圖 60
圖4-3 Device A1-A3 EL spectra 61
圖4-4 Device A1-A3 發光效率圖 61
圖4-5 Device A4 (a).EL光譜(b).發光效率圖(c).亮度圖(d).CIE色度座標 62
圖4-6 Device B 元件結構圖 64
圖4-7 Device B 電荷載子的傳輸機制示意圖 64
圖4-8 Device B 三重態激子的傳輸機制示意圖 65
圖4-9 Device B1-B3 (a).EL光譜(b).發光效率圖(c).亮度圖(d).CIE色度座標 65
圖4-10 Device C1 元件結構圖 67
圖4-11 Device C1之(a).EL光譜圖(b).發光效率圖(c).CIE色度座標 68
圖4-12 Device C2 元件結構圖 69
圖4-13 Device C2之(a).EL光譜圖(b).發光效率圖(c).CIE色度座標 70
圖4-14 Device D 元件結構圖 71
圖4-15 Device B1-B3 (a).EL光譜(b).發光效率圖(c).亮度圖 72
圖4-16 Device D3之CIEx和CIEy座標 74

[1].J. Z. Zhu, W. L. Li, and B. Chua, “Non-doped-type white organic light-emitting diodes for lighting purpose”, Appl. Phys. Lett., vol. 130, p. 865 (2010).
[2].Y. Fukuda, T. Watanabe, and T. Wakimoto, “An organic LED display exhibiting pure RGB colors’’, Synth. Met., vol. 111, p. 111 (2000).
[3].C. D. Müller, A. Falcou, and N. Reckefuss, “Multi-colour organic light-emitting displays by solution processing”, Nature, vol. 421, p. 829 (2003).
[4].Y. Xiong, W. Xu, C. Li, “Utilizing white OLED for full color reproduction in flat panel display”, Org. Electron, vol. 9, p. 533 (2008).
[5].B. D, Andrade, and J. J. Brown, “White phosphorescent organic light emitting devices for display applications”, Proc. Article, vol. 6225, p. 622514 (2006).
[6].C. W. Tang, and S. A. V. Slyke, “Organic electroluminescent diodes”, Appl. Phys. Lett., vol.51, p. 913 (1987).
[7].J. H. Burroughes, D. D. C. Bradley, A. R. Brown, R. N. Marks, K. Mackay, R. H. Friend, P. L. Burns, and A. B. Holmes, “Light-emitting diodes based on conjugated polymers”, Nature, vol.347, p. 539 (1990).
[8].J. H. Burroughes, D. D. C. Bradley, A. R. Brown, R. N. Marks, K. Mackay, R. H. Friend, P. L. Burns, and A. B. Holmes, “Light-emitting diodes based on conjugated polymers”, Nature, vol. 347, p. 539 (1990).
[9].C. J. Humphreys, “Solid-State Lighting”, MRS Bulletin, vol.33, p. 459 (2008).
[10].S. Reineke, F. Lindner, G. Schwartz, N. Seidler, K. Walzer, B. Lussem, and K. Leo, “White organic light-emitting diodes with fluorescent tube efficiency”, Nature, vol.459, p.234 (2009).
[11].A. H. Tullo, Chemical &; Engineering News, vol.86, p. 20 (2008).
[12].Q. Wang, J. Ding, D. Ma, Y. Cheng, L. Wang, and F. Wang, “Manipulating charges and excitons within a single-host system to accomplish efficiency/CRI/color-stability trade-off for hhigh-performance OWLEDs”, Advanced Materials, vol. 21, p. 2397 (2009).
[13].C. H. Chuen and Y. T. Tao, “Highly-bright white organic light-emitting diodes based on a single emission layer”, Appl. Phys. Lett., vol.81, p. 4499 (2002).
[14].J. Kido, H. Shionoya, and K. Nagai, “Single-layer white light-emitting organic electroluminescent devices based on dye-dispersed poly(N-vinylcarbazole)”, Appl. Phys. Lett., vol.67, p. 2281 (1995).
[15].Y. W. Ko, C. H. Chung, and J. H. Lee, “ Efficient white organic light emission by single emitting layer”, Thin Solid Films, vol. 426, p. 246 (2003).
[16].Y. S. Wu, S. W. Hwangb, and H. H. Chena, “Efficient white organic light emitting devices with dual emitting layers”, Thin Solid Films, vol. 488, p. 265 (2005).
[17].K. O. Cheon and J. Shinara, “Combinatorial fabrication and study of doped-layer-thickness-dependent color evolution in bright small molecular organic light-emitting devices”, Appl. Phys. Lett., vol. 83, p. 2073 (2003).
[18].K. O. Cheon and J. Shinara, “Bright white small molecular organic light-emitting devices based on a red-emitting guest–host layer and blue-emitting 4,40-bis.2,20-diphenylvinyl-1, 10-biphenyl”, Appl. Phys. Lett., vol. 81, p.1738 (2002).
[19].C. W. Tang and S. A. Van Slyke, “Organic electroluminescent diodes”, Appl. Phys. Lett., vol. 51, p. 913 (1987).
[20].C. Adachi, S. Tokito, T. Tsutsui, and S. Saito, “Organic electroluminescent device with a three-layer structure”, Jpn. J. Appl. Phys., vol. 27, p. L713 (1988).
[21].C. Adachi, T. Tsutsui, and S. Saito, “Confinement of charge carriers and molecular excitons within 5‐nm‐thick emitter layer in organic electroluminescent devices with a double hetero structure”, Appl. Phys. Lett., vol. 57, p. 531 (1990).
[22].D. F. Williams and M. Schadt, “A simple organic declrolumiwc Rlt diode”, Proc. Ins. Electrical and Electron. Eng., vol. 58, p. 476 (1970).
[23].J. Kido, K. Hongawa, K. Okuyama, and K. Nagai, “White light‐emitting organic electroluminescent devices using the poly(N‐vinylcarbazole) emitter layer doped with three fluorescent dyes”, Appl. Phys. Lett., vol. 64, p. 815 (1994).
[24].A. R. Duggal, J. J. Shiang, C. M. Heller, and D. F. Foust, “Organic light-emitting devices for illumination quality white light”, Appl. Phys. Lett., vol. 80, p. 3470 (2002).
[25].A. Mikami, Y. Mizuno, and S. Takeda, “High efficiency ultraviolet light emitting organic devices and its application to white light source”, SID Symp. Digest Tech. Pap. , vol. 39, p. 215 (2008).
[26].Y. B. Yuan, S. Li, Z. Wang, H. T. Xu, and X. Zhou, “White organic light-emitting diodes combining vacuum deposited blue electrophosphorescent devices with red surface color conversion layers”, Opt. Express, vol. 17, vol. 3, p. 1577 (2009).
[27].J. J. G. Casares, M. T. M. Romero, L. Camacho, B. C. Martinez, D. Cadd, C. Pearson, and M. C. Petty, “Stable white light emission from an externally modified organic light-emitting device”, Displays, vol. 31, p. 181 (2010).
[28].S. Chen and H. S. Kwok, “Top-emitting white organic light-emitting diodes with a color conversion cap layer”, Org. Electron., vol. 12, p. 677 (2011).
[29].N. Juharia, W. H. A. Majidb, and Z. A. Ibrahimb, “Degradation of single layer MEH-PPV organic light emitting diode (OLED)”, Inst. Electrical and Electron. Eng., p. 112 (2006).
[30].T. L. Chiu, J. H. Lee, C. C. Chao, M. K. Leung, D. H. Wan, and H. L. Chen, “Low reflectance white-OLED with Alq3 as the single emitter”, Int. Display Res. Conference (IDRC), p. 213 (2008).
[31].L. Aubouy, P. Gerbier, C. Gu´erin, N. Huby, L. Hirsch, and L. Vignau, “Study of the influence of the molecular organization on single-layer OLEDs’ performances”, Synth. Met., vol. 157, p. 91 (2007).
[32].J. Dresner, “Double injection electroluminescence in anthracene”, RCA Rev., vol. 30, p. 322 (1969).
[33].W. Helfrich and W. G. Schneidere, “Recombination radiation in anthracene crystals”, Phys. Rev. Lett., vol. 14, p. 229 (1965).
[34].D. F. Williams and M. Schadt, “A simple organic electroluminescent diode”, Proc. IEEE, vol. 58, p. 476 (1970).
[35].Y. Shirota, Y. Kuwabara, and H. lnada, “Multilayered organic electroluminescent device using a novel starburst molecule, 4,4’,4”-tris(~-methylphenylphenylamino)tripheny~amine, as a hole transport material”, Appl. Phys. Lett., vol. 65, p. 807 (1994).
[36].C. Hosokawa, H. Higashi, H. Nakamura, and T. Kusumoto, “Highly efficient blue electroluminescence from a distyrylarylene emitting layer with a new dopant”, Appl. Phys. Lett., vol. 67, p. 3853 (1995).
[37].M. A. Baido, S. Lamansky, P. E. Burroes, M. E. Thompson, and S. R. Forrest, “Very high-efficiency green organic light-emitting devices based on electrophosphorescence”, Appl. Phys. Lett., vol. 75, p. 4 (1999).
[38].T. Tsuyoshi, H. KOhei, and T. Naoki, “Accelerated hole transfer by double-layered metal phthalocyanine thin film for effective electroluminescence”, Appl. Phys. Let., vol. 70, p. 762 (1997).
[39].C. S. Woo, C. K. Hyuk, J. Jin, S. H. Lee, K. J. Joo, and K. H. Ki, “Highly flexible, transparent and low resistance IZO-Ag-IZO multilayer electrode for flexible OLEDs”, Proc. Int. Meeting on Inf. Display, vol. 8, p. 609 (2008).
[40].L. Hui, Y. Junsheng, W. Nana, H. Chunhua, and J. Yadonga, “Flexible organic light-emitting diodes with improved performance by insertion of an UV-sensitive layer”, J. Vac. Sci. Technol. B, vol. 26, no. 4, p. 1379 (2008).
[41].M. S. Weaver, L. A. Michalski, K. Rajan, M. A. Rothman, J. A. Silvernail, J. J. Brown, P. E. Burrows, G. L. Graff, M. E. Gross, P. M. Martin, M. Hall, E. Mast, C. Bonham, W. Bennett, and M. Zumhoff, “Organic light-emitting devices with extended operating lifetimes on plastic substrates”, Appl. Phys. Lett., vol. 81, p. 2929 (2002).
[42].Y. Yang, E. Westerweele, C. Zhang, P. Smith, and A. J. Heeger, “Enhanced performance of polymer light‐emitting diodes using high‐surface area polyaniline network electrodes”, J. Appl. Phys., vol. 77, p. 694 (1995).
[43].L. M. Wang, Y. J. Chen, and J. W. Liao, “Characteristics of indium-tin oxide thin films grown on flexible plastic substrates at room temperature”, J. Phys. Chem. Solids, vol. 69, p. 527 (2008).
[44].C. Decker, “UV-radiation curing chemistry”, Pigment &; Resin Technol., vol. 30, p. 278 (2001).
[45].V. Vasu and A. Subrahmanyam, “Reaction kinetics of the formation of indium tin oxide films grown by spray pyrolysis”, Thin Solid Films, vol. 193, p. 696 (1990).
[46].C. C. Wu, C. I. Wu, J. C. Sturm, and A. Kahn, “Surface modification of indium tin oxide by plasma treatment: An effective method to improve the efficiency, brightness, and reliability of organic light emitting devices”, Appl. Phys. Lett., vol. 70, p. 1348 (1997).
[47].K. Furukawa, Y. Terasaka, H. Ueda, and M. Mtsumura, “Effect of a plasma treatment of ITO on the performance of organic electroluminescent devices”, Synth. Met., vol. 91, p. 99 (1997).
[48].Z. Gao, J. Zhong, J. Yu, and Y. Jiang, “Study on lifetime of high brightness green organic light-emitting devices”, Int. Soc. Opt. and Photonics, vol. 7658, p. 76583M (2010).
[49].Q. Xue, G. Xie, P. Chen, J. Lu, D. Zhang, Y. Tang, Y. Zhao, J. Hou, and S. Liu, “White organic light-emitting devices with a bipolar transport layer between blue fluorescent and yellow phosphor-sensitized-fluorescent emitting layers”, Synth. Met., vol. 160, p. 829 (2010).
[50].H. Wang, K. P. Klubek, and C. W. Tang, “Current efficiency in organic light-emitting diodes with a hole-injection layer”, Appl. Phys. Lett., vol. 93, p.093306 (2008).
[51].Y. Cao, G. Yu, C. Zhang, R. Menon, and A. J. Heeger, “Polymer light-emitting diodes with polyethylene dioxythiophene–polystyrene sulfonate as the transparent anode”, Synth. Met., vol. 87, p. 171 (1997).
[52].S. Kirchmeyer and K. Reuter, “Scientific importance, properties and growing applications of poly(3,4-ethylenedioxythiophene)”, J. Mater. Chem., vol. 15, p. 2077 (2005).
[53].J. W. Ma, Z. Liang, C. Jin, X. Y. Jiang, and Z. L. Zhang, “Enhanced power efficiency for white OLED with MoO3 as hole injection layer and optimized charge balance”, Solid State Commun., vol. 149, p. 214 (2009).
[54].X. Zhou, M. Pfeiffer, J. Blochwitz, A. Werner, A. Nollau, T. Fritz, and K. Leo, “Very-low-operating-voltage organic light-emitting diodes using a p-doped amorphous hole injection layer”, Appl. Phys. Lett., vol. 78, p. 410 (2001).
[55].G. He, O. Schneider, D. Qin, X. Zhou, M. Pfeiffer, and K. Leo, “Very high-efficiency and low voltage phosphorescent organic light-emitting diodes based on a p-i-n junction”, J. Appl. Phys., vol. 95, p. 5773 (2004).
[56].S. Tokito and Y. Taga, “Organic electroluminescent devices fabricated using a diamine doped MgF2 thin film as a hole‐transporting layer”, Appl. Phys. Lett., vol. 66, p. 673 (1995).
[57].E. Han, I. Bo, Y. Niidome, and M. Fujihira, “Observation of crystallization of vapor-deposited TPD films by AFM and FFM”, Chem. Lett., vol. 23, p. 969 (1994).
[58].G. Xie, Z. Zhang, Q. Xue, S. Zhang, Y. Luo, L. Zhao, Q. Wu, P. Chen, B. Quan, Y. Zhao, and S. Liu, “Tailoring the efficiencies and spectra of white organic light-emitting diodes with the interlayers”, J. Phys. Chem. C, vol. 115, p. 264 (2011).
[59].J. Shi and C.W. Tang, “Doped organic electroluminescent devices with improved stability”, Appl. Phys. Lett., vol. 70, p. 1665 (1997).
[60].S. J. Lee, J. H. Seo, G. Y. Kim, and Y. K. Kim, “A study on the phosphorescent blue organic light-emitting diodes using various host materials”, Mol. Cryst. Liq., vol. 507, p. 345 (2009).
[61].H. Kanai, S. Ichinosawa, and Y. Sato, “Effect of aromatic diamines as a cathode interface layer”, Synth. Met., vol.91, p. 195 (1997).
[62].C. Adachi, R. C. Kwong, P. Djurovich, V. Adamovich, M. A. Baldo, M. E. Thompson, and S. R. Forrestc, “Endothermic energy transfer: A mechanism for generating very efficient high-energy phosphorescent emission in organic materials”, Appl. Phys. Lett., vol. 79, p. 2082 (2001).
[63].R. J. Holmes, S. R. Forrest, Y. J. Tung, R. C. Kwong, J. J. Brown, S. Garon and M. E. Thompson, “Blue organic electrophosphorescence using exothermic host–guest energy transfer”, Appl. Phys. Lett., vol. 82, p. 2422 (2003).
[64].Y. S. Seo and D. G. Moon, “Highly efficient blue phosphorescent organic light-emitting devices using simple structures with thin 1,1-bis[(di-4-tolyamino)phenyl]cyclohexane layers”, Synth. Met., vol. 160, p. 113 (2010).
[65].N. Chopra, J. Lee, Y. Zheng, S. H. Eom, J. Xue, and F. So, “Effect of the charge balance on high-efficiency blue-phosphorescent organic light-emitting diodes”, ACS Appl. Mater. Interfaces, vol. 1, p. 1169 (2009).
[66].S. J. Lee, J. H. Seo, J. H. Seo, G. Y. Kim, Y. Y. Jin, and Y. K. Kim, “A study on the phosphorescent blue organic light-emitting diodes using triplet exciton blocking layer”, J. Nanoscience and Nanotechnology, vol. 9, p. 7044 (2009).
[67].S. J. Yeh, M. F. Wu, C. T. Chen, Y. H. Song, Y. Chi, M. H. Ho, S. F. Hsu, and C. H. Chen, “New dopant and host materials for blue-light-emitting phosphorescent organic electroluminescent devices”, Adv. Mater., vol. 17, No.3, p. 285 (2005).
[68].T. Tsuboi, S. W. Liu, M. F. Wu, and C. T. Chen, “Spectroscopic and electrical characteristics of highly efficient tetraphenylsilane-carbazole organic compound as host material for blue organic light emitting diodes”, Org. Electron., vol. 10, p. 1372 (2009).
[69].D. Freemajrn, and C. White, “The structure and characteristics of the fluorescent metal chelates of o,o’-Dihydroxyazo compounds”, J. Am. Chem. Soc., vol. 78, p. 2678 (1956).
[70].L. Xiao , S. J. Su , Y. Agata , H. Lan , and J. Kido , “Nearly 100% internal quantum efficiency in an organic blue-light electrophosphorescent device using a weak electron transporting material with a wide energy gap”, Adv. Mater., vol. 21, p. 1271 (2009).
[71].N. Chopra, J. Lee, J. Xue, and F. So, “High-efficiency blue emitting phosphorescent OLEDs”, IEEE Trans. on Electron Devices, vol. 57, p. 101 (2010).
[72].G. He, M. Pfeiffer, K. Leo, M. Hofmann, J. Birnstock, R. Pudzich and J. Salbeck, “High-efficiency and low-voltage p-i-n electrophosphorescent organic light-emitting diodes with double-emission layers”, Appl. Phys. Lett., vol. 85, p. 3911 (2004).
[73].K. R. Choudhury, J. h. Yoon, and F. So, “LiF as an n-dopant in Tris(8-hydroxyquinoline) aluminum thin films”, Adv. Mater., vol. 20, p. 1456 (2008).
[74].J. Huang, Z. Xu, and Y. Yang, “Low-work-function surface formed by solution-processed and thermally deposited nanoscale layers of cesium carbonate”, Adv. Mater., vol. 17, p. 1966 (2007).
[75].M. Stössel, J. Staudigel, F. Steuber, J. Simmerer, and A. Winnacker. “Impact of the cathode metal work function on the performance of vacuum-deposited organic light emitting-devices”, Appl. Phys. A, vol. 68, p. 387 (1999).
[76].Y. Kawamora, S. Yanagida, and S. R. Forrest, “Energy transfer in polymer electrophosphorescent light emitting devices with single and multiple doped luminescent layers”, J. Appl. Phys., vol. 92, p. 87 (2002).
[77].M. C. Gather , A. Köhnen , and K. Meerholz, “White organic light-emitting diodes”, Adv. Mater., vol. 23, p. 233, (2011).
[78].J. Kido, M. Kimura, and K. Nagai, “Multilayer white light-emitting organic electroluminescent device”, Science, vol. 267, p. 1332 (1995).
[79].T. Shiga, H. Fujikawa, and Y. Taga, “Design of multiwavelength resonant cavities for white organic light-emitting diodes”, J. Appl. Phys., vol. 93, p. 19 (2003).
[80].J. C. Scott, J. H. Kaufman, P. J. Brock, R. Dipietro, J. Salem, and J. A. Goitia, “ Degradation and failure of MEH-PPV light-emitting diodes”, J. Appl. Phys., vol. 79, p. 2745 (1996).
[81].Y. S. Tsai, S. H. Wang, S. Y. Chen, S. Y. Su, and F. S. Juang, “Efficiency improvement of flexible fluorescent and phosphorescent organic light emitting diodes by inserting a spin-coating buffer layer”, Thin Solid Films, vol. 517, p. 5338 (2009).
[82].S. Zhang, Z. Liu, X. Wang, S. Yue, Z. Zhang, Q. Y. Wu, G. H. Xie, Q. Xue, Y. Chen, P. Wang, R. Guo, D. L. Qu, Y. Zhao, and S. Y. Liu, “White organic light-emitting diodes based on yellow phosphorescence iridium complex and a high-efficiency blue fluorescence”, Thin Solid Films, vol. 537, p. 221 (2013).
[83].Q. Wu, S. Zhang, S. Yue, Z. Zhang, G. Xie, Y. Zhao, and S. Liu, “Enhanced efficiency in single-host white organic light-emitting diode by triplet exciton conversion”, J. Lumin., vol. 143, p. 108 (2013).
[84].X. H. Wang, S. M. Zhang, Z. Y. Liu, S. Z. Yue, Z. S. Zhang, Y. Chen, G. H. Xie, Q. Xue, Y. Zhao, and S. Y. Liu, “Hybrid white organic light-emitting diodes with improved color stability and negligible efficiency roll-off based on blue fluorescence and yellow phosphorescence”, J. Lumin, vol. 137, p. 59 (2013).
[85].M. A. Baldo, C. Adachi, and S. R. Forrest, “Transient analysis of organic electrophosphorescence. II. Transient analysis of triplet-triplet annihilation”, Phys. Rev. B, vol. 62, p. 10967 (2000).
[86].D. H. Lee, S. J. Lee, J. R. Koo, H. W. Lee, S. E. Lee, H. J. Yang, J. Park, and Y. K. Kim, “Improved efficiency and lifetime for green phosphorescent organic light-emitting diodes using charge control layer”, Display, vol. 35, p. 79 (2014).
[87].C. H. Hsiao, S.W. Liu, C. T. Chen, J. H. Lee, “Emitting layer thickness dependence of color stability in phosphorescent organic light-emitting devices”, Org. Electron., vol. 11, p. 1500 (2010).
[88].Y. H. Son, M. J. Park, Y. J. Kim, J. H. Yang, J. S. Park, and J. H. Kwon, “Color stable phosphorescent white organic light-emitting diodes with double emissive layer structure”, Org. Electron., vol. 14, p. 1183 (2013).