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对于RGB有机电致发光器件(OLEDs), 蓝光非常重要. 在现有各种蓝光材料中, 聚芴(PFO)非常稳定且荧光量子效率可达80%, 但它有一个非常大的缺点: 电致发光会产生异常绿光带. 这严重影响了PFO相关器件的饱和色纯度. 本文使用分子基磁性材料Fe(NH2trz)3·(BF4)2掺杂PFO方法, 解决了这一难题. 以ITO为衬底, 制作了结构为ITO/PEDOT: PSS/PFO: Fe(NH2trz)3·(BF4)2/CsCl/Al的器件. 报道了利用Fe(NH2trz)3·(BF4)2特殊的电子自旋态调制PFO的光电特性, 实现了PFO的强烈纯正蓝光发射. 详细研究了Fe(NH2trz)3·(BF4)2对PFO光电特性的影响. 在4 V至9 V电压的偏置下, 没有Fe(NH2trz)3·(BF4)2的器件, 发出特别异常的绿光. 然而, 与此形成明显对照的是: Fe(NH2trz)3·(BF4)2掺杂的器件发出强烈的本征蓝光; PFO绿色发光带被成功压制; 随着电压的变化, 器件光谱的蓝光部分在整个EL谱所占比例没有改变. 运用光电磁一体化测量技术, 进一步研究了PFO掺杂Fe(NH2trz)3·(BF4)2器件的磁发光(MEL)和磁电导(MC)效应. 发现PFO: Fe(NH2trz)3·(BF4)2和纯PFO薄膜内都没有激基缔合物产生. 运用发光动力学理论, 分析了Fe(NH2trz)3·(BF4)2阻断PFO异常绿光发射的机理.Since the breakthrough by Tang et al. in 1987, organic light-emitting devices (OLEDs) have attracted extensive attention in the industries and academic research communities. OLEDs have many promising characteristics, such as self-illumination, lower power consumption, easy fabrication and so on. It has a broad development prospect in high resolution display and other fields. For RGB color OLED display technology, blue light organic material is very important. Polyfluorene (PFO) is a kind of rigid planar biphenyl structure compound in all kinds of OLEDs blue light materials. However, PFO has a very big disadvantage: the long wave shift of the light-emitting peak of the electroluminescent device will produce the green light-emitting band that should not have appeared. This seriously affects the saturation color purity of PFO devices, and also seriously restricts the industrialization process. In this paper, the molecular magnetic material [Fe(NH2trz)3· (BF4)2] is used to solve this problem. ITO/PEDOT:PSS (30 nm)/PFO:Fe(NH2trz)3·(BF4)2 (65 nm)/CsCl (0.6 nm)/Al (120 nm) devices were fabricated on ITO glass substrate. It is the first time to report the strong pure blue emission of PFO by using the special electronic spin state modulation of Fe(NH2trz)3·(BF4)2. The influence of Fe(NH2trz)3·(BF4)2 on the photoelectric properties of PFO was studied in detail by analyzing the PL and EL characteristics of PFO and PFO:Fe(NH2trz)3·(BF4)2. Under the bias voltage of 4 V to 9 V, the device without doping Fe(NH2trz)3·(BF4)2 emits very strong green light. The central peak wavelength is 553 nm, and the color coordinates are (0.33, 0.45). Moreover, with the constant change of voltage, the green light-emitting band is always much larger than the blue light-emitting band. However, the obvious difference is that Fe(NH2trz)3·(BF4)2 doped device emits strong blue light, the peak wavelength is 438 nm, and the color coordinates (0.23, 0.22), which is completely consistent with the peak wavelength of the PL spectrum of the PFO film; the green light-emitting band of the PFO is successfully suppressed; with the change of the electric voltage, the proportion of the blue light part of the device spectrum in the whole EL spectrum is almost unchanged. The photoconductivity effect of undoped Fe(NH2trz)3·(BF4)2 device is further studied by means of the integrated opto-electro-magnetic measurement technology. Under different bias voltage, it is found that there is almost no excimer in PFO:Fe(NH2trz)3·(BF4)2. This study solves the problem of green light of polyfluorene, which has puzzled the industry for many years, and provides a reliable way for the industrialization of polyfluorene used in blue OLED. The mechanism of Fe(NH2trz)3·(BF4)2 blocking the abnormal green emission of PFO was discussed by using the theory of luminescence dynamics.
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Keywords:
- organic light-emitting devices /
- polyfluorene /
- molecular based magnetic material /
- magnetic EL and magnetic conductivity
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图 1 (a)器件结构; (b)磁效应测试原理示意图
Fig. 1. Schematic description of the device structure (a) and the device fabricated for the MEL measurements (b).
图 2 Fe(NH2trz)3·(BF4)2合成路线和材料分子结构示意图
Fig. 2. Schematic description of synthetic route and molecular structures of the materials studied.
图 3 不同电压下, 器件ITO/PEDOT: PSS/PFO/CsCl/Al的归一化电致发光EL谱
Fig. 3. Normalized EL spectra of the device with ITO/PEDOT: PSS/PFO/CsCl/Al.
图 4 PFO薄膜的PL谱(红色)和8 V偏置电压的 EL谱(黑色)
Fig. 4. PL(red)and EL(black)spectra of the PFO film at 8 V.
图 5 (a)器件ITO/PEDOT: PSS/PFO: Fe(NH2trz)3·(BF4)2/CsCl/Al的电致发光EL谱; (b)该器件的电流-电压-亮度曲线
Fig. 5. (a) EL spectra of the device with ITO/PEDOT: PSS/PFO: Fe(NH2trz)3·(BF4)/CsCl/Al; (b) I-V-L characteristics response of the device
图 6 PFO: Fe(NH2trz)3·(BF4)2薄膜的PL谱(紫色)和7 V偏置电压的 EL谱(青色)
Fig. 6. PL(purple)and EL(ching)spectra of the PFO: Fe(NH2trz)3·(BF4)2 film at 7 V.
图 7 不同电压下器件ITO/PEDOT: PSS/PFO: Fe(NH2trz)3·(BF4)2/CsCl/Al的磁发光曲线(a)和MC曲线(b)
Fig. 7. MEL (a) and MC (b) of the device with ITO/PEDOT: PSS/ PFO: Fe(NH2trz)3·(BF4)2/CsCl/Al under different voltage
图 8 不同电压下器件ITO/PEDOT: PSS/ PFO/CsCl/Al的磁发光曲线 (a)和MC曲线(b)
Fig. 8. MEL (a) and MC (b) of the device with ITO/PEDOT: PSS/ PFO/CsCl/Al under different voltage.
图 9 Fe(NH2trz)3·(BF4)2耦合“剪断”PFO在电致发光过程中被氧化为芴酮机理图
Fig. 9. Mechanism diagram of Fe(NH2trz)3·(BF4)2 coupling cutting PFO oxidation to fluorenone in electroluminescence.
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[1] Tang C W, VanSlyke S A V 1987 Appl. Phys. Lett. 51 913
Google Scholar
[2] Ghosh I, Khamrai J, Savateev A K 2019 Science 365 360
Google Scholar
[3] 肖心明, 朱龙山, 关宇, 华杰, 王洪梅, 董贺, 汪津 2020 69 047202
Google Scholar
Xiao X M, Zhu L S, Guan Y, Hua J, Wang H M, Dong H, Wang J 2020 Acta Phys. Sin. 69 047202
Google Scholar
[4] Niu L B, Chen L J, Chen P, Cui Y T, Zhang Y, Shao M, Guan Y X 2016 RSC Adv. 6 111421
Google Scholar
[5] Burroughes J H, Bradley D C, Brown A R, Marks R N, Mackay K, Richard H F, Burns P L 1990 Nature 347 539
Google Scholar
[6] Stefan B, Christophe E, Andrew C G, Emil J W, Marsitzky D, Alexander P, Sepas Setayesh, Leising G, Mullen K 2001 Synth. Met. 125 73
Google Scholar
[7] Marystela F, Clarissa A O, Angelita M M, Andressa M A, José A G, Leni A, Osvaldo N J 2007 J. Polym. Res. 14 39
Google Scholar
[8] Inaoka S, Advincula R 2002 Macromolecules 35 2426
Google Scholar
[9] Mark T B, Michael I, Edmund P W, Wei W W, Lisa W K 1999 Proc. SPIE, Light-Emitting Diodes: Research, Manufacturing, and Applications III, 3621 93
[10] Niu L B, Chen L J, Tao S L, Guan Y X 2018 J. Mol. Liq. 259 411
Google Scholar
[11] Gong X, Iyer P K, Moses D, Bazan G C, Heeger A J, Xiao S 2003 Adv. Funct. Mater. 13 325
Google Scholar
[12] Emil J W, Guentner R, Scanducci P D, Ullrich S 2002 Adv. Mater. 14 374
[13] Mathieu S, Emmanuelle H, Christophe E, Dirk M, Andrew C G, Müllen K, Brédas J L, Roberto L, Philippe L 2004 Chem. Mater. 16 994
Google Scholar
[14] 姜鸿基, 万俊华, 黄维 2008 中国科学: 化学 38 183
Jiang H J, Wan J H, Huang W 2016 Science in China: Chemistry 46 037001 (in Chinese)
[15] Malcolm A H, Izar C B, Christopher M P, Kulmaczewski R 2019 Inorg. Chem. 58 9811
Google Scholar
[16] Sun H Y, Meng Y S, Liu T 2019 Chem. Commun. 55 8359
Google Scholar
[17] Wang C F, Li R F, Chen X Y, Wei R J, Zheng L S, Tao J 2015 Angew. Chem. 54 1574
Google Scholar
[18] Kitts C C, Vanden B D 2007 Polymer 48 2322
Google Scholar
[19] Bradley D D C, Grell M, Lo ng, X, Mellor H, Grice A 1998 Proc. SPIE 3145 254
[20] Klarner G, Davey M. H, Chen W D, Scott J C, Miller 1998 R D Adv. Mater. 10 993
Google Scholar
[21] List J W, Guentner R, Freitas P S, Scherf U 2002 Advanced Materials 14 374
[22] Gaal M, List E J W, Scherf U 2003 Macromolecules 36 4236
Google Scholar
[23] Gamerith S, Gaal M, Romaner L, Nothofer H G, Guntner R, Freitas P S, Scherf U, List E J W 2003 Synth. Met. 139 855
Google Scholar
[24] Kappaun S, Scheiber H, Trattnig R, Zojer E, List E J W, Slugovc C 2008 Chem. Commun. 51 70
[25] Gong X, Iyer P K, Moses D, Bazan G C, Heeger A J, Xiao S S 2003 Advanced Funct. Materials 13 325
[26] Lapres A, Silvia T, Manuel H, Alfonso S 2013 Chem. Commun. 49 288
Google Scholar
[27] 白凤莲 1985 化学通报 6 31
Bai F L 1985 Chemistry Bulletin 6 31
[28] Förster T, Kasper K 1954 Phys. Chem. N. F. 1 275
Google Scholar
[29] Yuan P S, Qiao X F, Yan D H, Ma D G 2019 J. Mater. Chem. C 7 1035
Google Scholar
[30] Xiang J, Chen Y B, Yuan D, Jia W Y, Zhang Q M, Xiong Z H 2016 Appl. Phys. Lett. 109 103301
Google Scholar
[31] 赵茜, 汤仙童, 潘睿亨, 许静, 屈芬兰, 熊祖洪 2019 科学通报 64 2514
Google Scholar
Zhao X, Tang X T, Pan R H, Qu F L, Xiong Z H 2019 Chin. Sci. Bull 64 2514
Google Scholar
[32] Xiang J, Chen Y B, Jia W Y, Chen L X, Lei Y L, Zhang Q M, Xiong Z H 2016 Org. Electron. 28 94
Google Scholar
[33] Zhao B, Zhang H, Miao Y Q, Wang Z Q, Gao L, Wang H, Hao Y Y, Xu B S, Li W L 2017 J. Mater. Chem. C 5 12182
Google Scholar
[34] Jiang F, Dong M Q, Wang Y N 2020 J. Magn. Magn. Mater. 497 165969
Google Scholar
[35] 刘俊娟, 魏增江, 常虹, 张亚琳, 邸冰 2016 65 067202
Google Scholar
Liu J J, Wei Z J, Chang H, Zhang Y L, Di B 2016 Acta Phys. Sin. 65 067202
Google Scholar
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