磷光掺杂聚合物能量传递的研究
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摘要
有机电致发光是最有前途的平板显示技术之一。聚合物／磷光体系电致发光已取得了一定进展,在效率和亮度上可以与小分子磷光器件相当。但是器件的稳定性还有待进一步提高,发光机理也还有待深入研究。本文重点研究了荧光和磷光染料掺杂聚合物中三线态激子和单线态激子的发光和能量传递以及磁场对电致发光的影响等问题,得到一些研究结果。
掺杂体系的发光机理主要以Forster和Dexter为主,但都要求母体的发射和客体的吸收有光谱重叠,而更多研究表明对于光谱重叠不是很明显的掺杂体系其电致发光很容易实现完全的能量传递,同样条件下的光致发光却转移不彻底,为进一步研究掺杂体系的发光机理采用惰性物质聚甲基丙烯酸甲酯(PMMA)为母体研究其电致发光光谱(EL)表明,没有光谱重叠也可以实现能量传递,这为我们选择OLED的母体材料大大扩大了范围。为研究这种机理在OLED器件中的作用,作了聚乙烯咔唑(PVK)为基质的同样器件并比较客体的发射,发现载流子俘获机理导致的发光随着电压升高而增强。
在Ir(ppy)3掺杂PVK体系EL研究中,我们发现,在低载流子注入时,EL谱中PVK的发射的相对强度要比PL谱PVK的发射强,这不符合Foster能量传递原理,从主体向客体的能量传递受到了阻碍。DCJTB掺杂PVK的EL发光中,也发现了类似的现象。这是由于Ir(ppy)3和DCJTB的HUMO和LUMO能级能够俘获电子和空穴,这些染料掺杂分子变成带负电荷或正电荷。束缚了载流子的掺杂分子与PVK的激子相互作用,降低了PVK激子向染料分子的能量传递几率,从而降低了染料激子的形成几率。给出了可能的存在的相互作用机制及作用过程。此外,双染料掺杂的电致发光器件中未发现这种情况。
初步探讨了Ir(ppy)3掺杂PVK在磁场和磁性纳米颗粒参与下的电致发光。在塞曼效应和轨道耦合作用下,单线态-三线态之间的能量传递增强Ir(ppy)3发光强度增大。
In recent years there has been much interest in polymer-based light-emitting diode (PLED), and intensive research has been devoting to their development due to their promising applications in display technology. Although great progress has made, there are still many arguments to the mechanisms concerned
Poly methyl methacrylate(PMMA), an inertia host material, was doped with 4-(dicyanomethylene)-2-t-buty-6-(1,1,7,7-tetramethyljulolidy-9-enyl)-4H-pyran(DCJTB), the electroluminescence-(EL) and phtotlu-minsecence(PL) were analysed. The distinct EL was observed but not the PL since no spectral overlap between the host and guest, which indicted that hole and electron direct recombine on the guest molecular by charge trapping. For comparison, similar device with (N-vinylcarbazole)(PVK) as a matrix material was studied, higher luminescence was observed from the PVK—based device due to the favorable hole transporting ability of PVK, but the luminescence increases slowly with applied voltage than the PMMA-based one, indicating that carrier trapping contributes more to its luminescence at a higher voltage, which agrees well with the carrier trapping mechanism.
According to the changes in the electroluminescence (EL) spectrum and the relative intensity of photoluminescence(PL) spectrum of PVK doped by Ir(ppy)3 and DCJTB, we also find that the relative intensity of the emission from dye rises with increasing biases. At low bias, the relative intensity of emission from PVK host is much higher than that in PL. Basing on the experimental results, the interaction between host-exciton and charged-trap is found. The interaction blocks the energy transfer from host to dye guest.
The electrophosphorescent organic light emitting diode with the structure of ITO/ PVK:Ir(ppy)3 (1:0.1%wt)/Al doped by magnetic nanopartical of iron were fabricated. Their electroluminescence properties were measured under an externalmagnetic field of 20 mT. Compared to the case of without magnetic field, the emission of Ir(ppy)3 increased. The results of experiment attributed to the Zeeman split of triplet state and hyperfine interactions of electrons and holes, which improving the energy transfer of singlet-triplet.
掺杂体系的发光机理主要以Forster和Dexter为主,但都要求母体的发射和客体的吸收有光谱重叠,而更多研究表明对于光谱重叠不是很明显的掺杂体系其电致发光很容易实现完全的能量传递,同样条件下的光致发光却转移不彻底,为进一步研究掺杂体系的发光机理采用惰性物质聚甲基丙烯酸甲酯(PMMA)为母体研究其电致发光光谱(EL)表明,没有光谱重叠也可以实现能量传递,这为我们选择OLED的母体材料大大扩大了范围。为研究这种机理在OLED器件中的作用,作了聚乙烯咔唑(PVK)为基质的同样器件并比较客体的发射,发现载流子俘获机理导致的发光随着电压升高而增强。
在Ir(ppy)3掺杂PVK体系EL研究中,我们发现,在低载流子注入时,EL谱中PVK的发射的相对强度要比PL谱PVK的发射强,这不符合Foster能量传递原理,从主体向客体的能量传递受到了阻碍。DCJTB掺杂PVK的EL发光中,也发现了类似的现象。这是由于Ir(ppy)3和DCJTB的HUMO和LUMO能级能够俘获电子和空穴,这些染料掺杂分子变成带负电荷或正电荷。束缚了载流子的掺杂分子与PVK的激子相互作用,降低了PVK激子向染料分子的能量传递几率,从而降低了染料激子的形成几率。给出了可能的存在的相互作用机制及作用过程。此外,双染料掺杂的电致发光器件中未发现这种情况。
初步探讨了Ir(ppy)3掺杂PVK在磁场和磁性纳米颗粒参与下的电致发光。在塞曼效应和轨道耦合作用下,单线态-三线态之间的能量传递增强Ir(ppy)3发光强度增大。
In recent years there has been much interest in polymer-based light-emitting diode (PLED), and intensive research has been devoting to their development due to their promising applications in display technology. Although great progress has made, there are still many arguments to the mechanisms concerned
Poly methyl methacrylate(PMMA), an inertia host material, was doped with 4-(dicyanomethylene)-2-t-buty-6-(1,1,7,7-tetramethyljulolidy-9-enyl)-4H-pyran(DCJTB), the electroluminescence-(EL) and phtotlu-minsecence(PL) were analysed. The distinct EL was observed but not the PL since no spectral overlap between the host and guest, which indicted that hole and electron direct recombine on the guest molecular by charge trapping. For comparison, similar device with (N-vinylcarbazole)(PVK) as a matrix material was studied, higher luminescence was observed from the PVK—based device due to the favorable hole transporting ability of PVK, but the luminescence increases slowly with applied voltage than the PMMA-based one, indicating that carrier trapping contributes more to its luminescence at a higher voltage, which agrees well with the carrier trapping mechanism.
According to the changes in the electroluminescence (EL) spectrum and the relative intensity of photoluminescence(PL) spectrum of PVK doped by Ir(ppy)3 and DCJTB, we also find that the relative intensity of the emission from dye rises with increasing biases. At low bias, the relative intensity of emission from PVK host is much higher than that in PL. Basing on the experimental results, the interaction between host-exciton and charged-trap is found. The interaction blocks the energy transfer from host to dye guest.
The electrophosphorescent organic light emitting diode with the structure of ITO/ PVK:Ir(ppy)3 (1:0.1%wt)/Al doped by magnetic nanopartical of iron were fabricated. Their electroluminescence properties were measured under an externalmagnetic field of 20 mT. Compared to the case of without magnetic field, the emission of Ir(ppy)3 increased. The results of experiment attributed to the Zeeman split of triplet state and hyperfine interactions of electrons and holes, which improving the energy transfer of singlet-triplet.
引文
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[41]Eley, D. D. and Spivey, D. J. Trans. Faraday Soc.,1960,56:1432.
[42]Eley, D. D. and Leslie, R. B. Nature,1963,147:898.
[43]Kemeney, G. and Rosenberg, B. J. Chem. Solids,1970,53:3549.
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[45]T. Tsutsui, M. J. Yang, et al. Jpn.J. Appl. Phys.,1999, Part 2,38:L1502.
[46]R. A. Keller, H. A. Rost, J. Chem. Phys.,1962,36:2640.
[47]G. Kemeny and B. Rosenberg, J. Chem. Phys.,1970,55:3549.
[48]BrownAR, Bradley DDC, Burroughes J H, et al. Appl. Phys. Lett.,1992,61:2793.
[49]Shi J, Tang C W. Appl. Phys. Lett.,1997,70:1665.
[50]Xiong.Gong, Jacek C. Ostrowski, et al. Adv.Funct.Mater.,2003,13:439.
[51]Xiong.Gong, Jacek C. Ostrowski, et al. Appl.Phys.lett.,2002,81:3711.
[52]Fangzhong Shen, Hong Xia, et al. Appl.Phys.lett.,2004,84:55.
[53]Huang Jinsong, Yang Kaixia, et al. Chinese Journal Of Liquid Crystals And Displays,1999,14: 1.
[54]P.Peumans, and S.R.Forrest. Appl.Phys.Lett.,2001,79:126.
[55]A.Elschner, F.Bruder, et al. Synth. Met.,.2000,139:111-112.
[56]G.Greczynski, Th. Kugler, et al. J.Electron Spectrosc. Related Phenom.,2001,121:1.
[57]P.Peumans, A.Yakimov et al. J.Appl.Phys.,,2003,93:3693.
[58]M.P.de Jong, L.J.van Ijzendoorn, et al. Appl.Phys.Lett.,2000,77:2255.
[59]J.Huang, P.F.Miller, et al. Synth. Met.,2003,139:569.
[60]Fangzhong Shen, Hong Xia, Chengbo Zhang, Yuguang Ma, et al. Appl.Phys.lett.,2004,1: 55-57.
[61]Xiong.Gong, Jacek C. Ostrowski, et al. Adv.Funct.Mater.,2003,13(6):439-443.
[62]Xiong.Gong, Jacek C. Ostrowski, et al. Appl.Phys.,2002,81:3711.
[63]K.Usgui. et al J. Electrochem Soc.,1992,139 (36):10.
[64]Klessinger M, e t al. New York:VCH Publishers,1995.
[65]Baldo M A, et al. Phy Rev B,1999,60:14422.
[66]Baldo M A, et al. Nature,2000,403:750.
[67]Groff R P, Merrifie R E, et al. Phys.Rev Lett.,1972,29:429.
[68]Groff R P, Suna A, et al. Phys. Rev. B,1974,9:2655.
[69]Kalinowski J,Cocchi M, et al. Phys.Rev.B,2004,70:5303.
[70]Odaka H,Okimoto Y, et al. Appl.Phys.Lett.,2006,88:3501.
[71]Desai P, Shakya P, et al. Phys.Rev.B,2007,75:4423.
[72]Desai P,Shakya P, et al. J.Appl.Lett.,2007,102:3710.
[73]Shakya P, Desai P, et al. J.Appl.Phys.,2008,103:3715.
[74]Veeraraghavan G, Nguyen T D, et al. Phys. Condes.Matter.,2007,19:6209.
[75]Wang Z,He Z H, et al. Acta Phys.Sin.,2007,56:2979 (in Chinese).
[76]Liu R,Lei Y L, et al. Sci.China Ser. G,2009,39:662 (in Chinese).
[77]磁性掺杂提升OLED发光效率[J].电子元件与材料,2008,2：53.
[78]Wu Y, Hu B, et al. Phys. Rev. B,2007,75:5214.
[79]Wang J, Hua J, et al. Acta Phys.Sin.,2009,58:7272 (in Chinese).
[2]J. Haaranen, et al. SID 95'Digest,1995:883.
[3]M. Aguilera, et al. SID 96'Digest,1996:125.
[4]W. A.Barrow, et al. SID 93'Digest,1993:761.
[5]W. A.Barrow, et al. Conf. Record of 1994 International Display Research Conf,1994:448.
[6]R. T. Tuenge. Asia Display,1995,95:279.
[7]Xu Xurong, Proceedings of 1994 EL,1994:42.
[8]C. W. Tang and S. A.Vanslyke. Organic electroluminescent diodes[J]. Appl. Phys. Lett.,1987, 51(12):913-915.
[9]C. Adachi, T. Tsutsui, and S. Saito. Blue lightemitting organic electroluminescent devices[J]. Appl. Phys. Lett.,1990,56 (9):799-801.
[10]李文连.有机电致发光显示器的产业化[J].发光快报,1995,6(1).
[11]H. Vestweber, W. Rieb. Abstract of Int. Conf. on EL of Mole. Mat. And Related Phen., P.96.
[12]S. R. Forrest, et al. Abstract of Int. Conf. on EL of Mole. Mat. And Related Phen., P.5
[13]C. Adachi, S. Tokito, T. Tsutsui and S. Saito. Electroluminescence in Organic Films with Three-Layer Structrue [J]. Jpn. J. Appl. Phys.,1988,27:L267.
[14]C. Adachi, T. Tsutsui and S. Saito. Organic electroluminescent device having a hole conductor as an emitting layer [J]. Appl. Phys. Lett.,1989,55 (15):1489-1491.
[15]C. Adachi, T. Tsutsui and S. Saito. Appl. Phys. Lett.,1990,57 (6):269.
[16]K. C. Kao and W.Hwang. Electrical Transport in Solids [M]. New York:Pergamon, P.486.
[17]C. Adachi, S. Tokito, M. Morikaw, T. Tsutsui and S. Saito. Springer Proceedings in Physics. Berlin:Springer-Verlag,1989,38:358.
[18]Sze,S.M. Physics of Semiconductor Devices [M].New York:John Wiley & Sons,1981:213.
[19]F. F., Forrest S. R., Shi Y. Q. and Steler W. H. Appl. Phys. Lett.,1990,56:674.
[20]J. H. Burroughes, D. D. C. Bradley, A. R. Brown, et al. Nature,1990,347:539.
[21]D. Braun and A. J. Heeger. Appl. Phys. Lett.,1991,58:1982.
[22]G. Gustafasson, Y. Cao, and A. J. Heeger, et al. Nature,1992,357:477.
[23]Grell M., Bradley D. D. C., Inbasekaran M., et al. Adv. Mater.,1997,7:798.
[24]Inbasekaran M., et al. US Patent,1998,5:777070.
[25]Fukuda M., Sawada K. and Yoshimo K., J. Polym. Sci. Polym.,1993,31:2465.
[26]Redecker M., Bradley D. D. C., et al. Adv. Mater.,1999,11:241.
[27]Ohmori Y., Uchida M., Muro K., et al. J PN. J. Appl. Phys.,1991,30:L1938.
[28]Ohmori Y., Uchida M., Muro K., et al. Solid State Commun.,1991,80:605.
[29]M. A. Baldo et al. Nature,1998,395:151.
[30]R. H. Friend, et al. Nature,1999,397:121.
[31]T. F. Guo, et al. Org. Electron,2000,1:15.
[32]S. Chang, et al. Appl. Phys. Lett.,2001,79:15.
[33]See, UNIAX Corporation. (http://www.uniax.com).
[34]Lee Change-Lyoul, et al. Appl. Phys. Lett.,2000,77:2280.
[35]Lamansky Sergey, Kwong Raymond C. Organic. Electronics,2001,2:53.
[36]Ma Yuguang, Zhou Xuemei, Shen Jiacong, et al. Appl. Phys. Lett.,1999,74:1361.
[37]Ma Yuguang, Chai Hsiuyi, et al. Chem Commun.,1998:2491-2492.
[38]Ma Y, Kai T, Wu Y. A. et al. Advan. Mater.,2000,12:433.
[39]Ma Yuguang, Che Chiming, et al. Advan. Mater.,1999,11:852.
[40]Ma Yuguang, Chan Winghan, et al. New J. Chem.,1999,23:263.
[41]Eley, D. D. and Spivey, D. J. Trans. Faraday Soc.,1960,56:1432.
[42]Eley, D. D. and Leslie, R. B. Nature,1963,147:898.
[43]Kemeney, G. and Rosenberg, B. J. Chem. Solids,1970,53:3549.
[44]J. S. Wilson, A. S. Dhoot, A. J. A. B. Seeley. Nature,2001,413:828.
[45]T. Tsutsui, M. J. Yang, et al. Jpn.J. Appl. Phys.,1999, Part 2,38:L1502.
[46]R. A. Keller, H. A. Rost, J. Chem. Phys.,1962,36:2640.
[47]G. Kemeny and B. Rosenberg, J. Chem. Phys.,1970,55:3549.
[48]BrownAR, Bradley DDC, Burroughes J H, et al. Appl. Phys. Lett.,1992,61:2793.
[49]Shi J, Tang C W. Appl. Phys. Lett.,1997,70:1665.
[50]Xiong.Gong, Jacek C. Ostrowski, et al. Adv.Funct.Mater.,2003,13:439.
[51]Xiong.Gong, Jacek C. Ostrowski, et al. Appl.Phys.lett.,2002,81:3711.
[52]Fangzhong Shen, Hong Xia, et al. Appl.Phys.lett.,2004,84:55.
[53]Huang Jinsong, Yang Kaixia, et al. Chinese Journal Of Liquid Crystals And Displays,1999,14: 1.
[54]P.Peumans, and S.R.Forrest. Appl.Phys.Lett.,2001,79:126.
[55]A.Elschner, F.Bruder, et al. Synth. Met.,.2000,139:111-112.
[56]G.Greczynski, Th. Kugler, et al. J.Electron Spectrosc. Related Phenom.,2001,121:1.
[57]P.Peumans, A.Yakimov et al. J.Appl.Phys.,,2003,93:3693.
[58]M.P.de Jong, L.J.van Ijzendoorn, et al. Appl.Phys.Lett.,2000,77:2255.
[59]J.Huang, P.F.Miller, et al. Synth. Met.,2003,139:569.
[60]Fangzhong Shen, Hong Xia, Chengbo Zhang, Yuguang Ma, et al. Appl.Phys.lett.,2004,1: 55-57.
[61]Xiong.Gong, Jacek C. Ostrowski, et al. Adv.Funct.Mater.,2003,13(6):439-443.
[62]Xiong.Gong, Jacek C. Ostrowski, et al. Appl.Phys.,2002,81:3711.
[63]K.Usgui. et al J. Electrochem Soc.,1992,139 (36):10.
[64]Klessinger M, e t al. New York:VCH Publishers,1995.
[65]Baldo M A, et al. Phy Rev B,1999,60:14422.
[66]Baldo M A, et al. Nature,2000,403:750.
[67]Groff R P, Merrifie R E, et al. Phys.Rev Lett.,1972,29:429.
[68]Groff R P, Suna A, et al. Phys. Rev. B,1974,9:2655.
[69]Kalinowski J,Cocchi M, et al. Phys.Rev.B,2004,70:5303.
[70]Odaka H,Okimoto Y, et al. Appl.Phys.Lett.,2006,88:3501.
[71]Desai P, Shakya P, et al. Phys.Rev.B,2007,75:4423.
[72]Desai P,Shakya P, et al. J.Appl.Lett.,2007,102:3710.
[73]Shakya P, Desai P, et al. J.Appl.Phys.,2008,103:3715.
[74]Veeraraghavan G, Nguyen T D, et al. Phys. Condes.Matter.,2007,19:6209.
[75]Wang Z,He Z H, et al. Acta Phys.Sin.,2007,56:2979 (in Chinese).
[76]Liu R,Lei Y L, et al. Sci.China Ser. G,2009,39:662 (in Chinese).
[77]磁性掺杂提升OLED发光效率[J].电子元件与材料,2008,2：53.
[78]Wu Y, Hu B, et al. Phys. Rev. B,2007,75:5214.
[79]Wang J, Hua J, et al. Acta Phys.Sin.,2009,58:7272 (in Chinese).