【作者】 杨光；

【导师】 侯延冰；

【作者基本信息】 北京交通大学 ， 光学， 2010， 硕士

【摘要】 有机自旋电子学在有机电致发光器件(Organic Light-Emitting Diode, OLED)的研究中起到越来越重要的作用。本论文运用旋涂和真空镀膜技术,利用传统半导体聚合物MEHPPV(2-甲氧基,5(2’-乙基己氧基)-1,4-苯撑乙烯撑)作为功能层,通过Fe薄膜对注入电子进行白旋极化、有机磁性材料二茂铁对注入空穴进行自旋极化以及制作Fe3O4/MEHPPV/Fe自旋阀结构对注入电子和空穴同时进行自旋极化等三个方面的实验,研究和讨论了器件的发光特性以及器件性能改变的机理。研究表明,(1)Fe磁性阴极的引入对于提高器件磁调控性能有一定的积极影响。在磁场的调制下,Fe薄层厚度为1 nm的器件性能较好,最大发光效率可达1.63 cd／A。我们认为根据Em和Merrifield理论,在磁场的调制下,三线态激子可以和自由载流子发生相互作用,从而引起单线态激子比例的提高,器件内自由载流子的数量增多,从而增加器件内部电流。(2)在25 mT的磁场调制下,掺杂了二茂铁的器件最大发光效率可达3.61 cd／A,亮度较无磁场调制时提高了约8%。我们分析认为,发光强度增加的是因为从二茂铁获得自旋极化的空穴和从阴极注入的未自旋极化的电子辐射复合的结果,在二茂铁内发生了单线态激子和三线态激子之间的系间转换,从而提升了单线态激子在所有激子中的比例。(3)Fe3O4/MEHPPV/Fe结构表现出了自旋阀特性。我们认为,在磁场的调制下,这种自旋阀结构的器件能够得到自旋极化方向相反的电子和空穴,在发光区形成有效的单线态激子,并复合发光。更多还原

【Abstract】 Organic spintronics plays a very important role in the research of OLED. In this thesis, we fabricated standard MEHPPV (poly(2-methoxy,5-(2’-ethylhexyloxy)-1,4-phenylene vinylene)) polymer devices with a Fe film or with Ferrocene dopant or with a organic spin-valve structure including Fe3O4/MEHPPV/Fe, by using spin-coating and conventional thermal evaporation in molecular vapor deposition system. We investigated the characteristics of the fabricated devices, and discussed the mechanisms for magnetic field dependence of the performance.Our experiment results show,1) Fe thin film can influence the devices performance positively. Tuned by magnetic field, the performance of the Fe thermal deposition with 1.0 nm nominal thickness is the most effective, the luminescence efficiency is 1.63 cd/A, maximally. One of the dominant mechanisms responsible for this performance is due to the interaction of free carriers with triplets within the devices through the mechanism proposed by Ern and Merrifield, which can cause the higher singlets proportion, and improve the amount of the free carriers within the devices and increase the current.2) Under the presence of the magnetic field of 25 mT, the luminescence efficiency of the device with ferrocene doping active layer reaches 3.61 cd/A maximally, and the EL enhancement is increased around 8%. We attribute the EL enhancement to the recombination of spin-polarized holes from ferrocene and non spin-polarized electrons from the A1 cathode in the doping devices. The magnetic field-dependent ratio of singlet induced by ferrocene should be due to singlet-triplet intersystem conversion upon the dispersion of the ferrocene.3) The performance of Fe3O4/MEHPPV/Fe shows spin-valve characteristic. We consider that magnetic field can polarize electrons and holes with anti-parallel configurations simultaneously, and then these polarized electrons and holes will form effective singlets in the polymers and recombine with photons.更多还原