OLEDs中多种微观机制共存的电致发光磁效应

发布时间：2018-01-26 04:08

本文关键词： 有机发光二极管电致发光磁效应超精细相互作用单重态激子分裂三重态-三重态激子淬灭　出处：《西南大学》2015年硕士论文　论文类型：学位论文

【摘要】：近年来,在不含任何磁性材料的有机光电器件(OLEDs)中出现的奇特的磁效应也引起了人们的广泛关注。研究人员对有机磁场效应的机理进行了深入的研究并提出了许多理论模型。但随着研究的深入,人们发现OLEDs的磁效应复杂多变,至今还没有一种微观机制能解释所有的实验现象。每一种机制只能部分解释器件的磁效应或某些特定材料组成的有机发光器件的磁效应,而对于一些奇特磁效应却不能很好的解释。因此,探究这些复杂磁效应的微观机制也就成为了研究人员关注的焦点之一本论文先针对掺杂型有机发光二极管的奇特电致发光磁效应及其影响因素进行了深入分析。通过改变掺杂浓度、注入电流密度和温度,研究器件磁发光效应的变化探究导致其复杂磁效应的微观机制。然后,在具有单重态激子裂变(STT)和三重态-三重态激子淬灭(TTA)性质的掺杂型有机发光二极管中,定性的研究了掺杂浓度对掺杂器件磁场效应的影响,试图探究STT和TTA两种微观机制间的竞争及其微观差异。本论文主要可分为以下几个部分：(1)首先,介绍了有机磁场效应的发展历程及其发展现状：之后详细介绍了有机发光二极管磁效应的研究进展以及提出的一些物理机制模型,如超精细相互作用模型、三重态-三重态激子淬灭模型、单重态激子裂变模型等。在本文的第二章主要介绍了有机发光二极管的制备技术和有机磁效应测试方法,以及在制备和测试器件过程中需要注意的一些问题。(2)在具有较高三重态激子能量的磷光材料mCP中掺入单重态与三重态激子能量共振的荧光染料Rubrene,制备了结构为ITO/CuPc/NPB/mCP:Rubrene/BCP/LiF/A1的掺杂型有机发光二极管,并测量了不同掺杂浓度下器件的磁场效应。并测量了不同掺杂浓度下器件的MEL。实验发现：掺杂器件的电致发光磁场效应(MEL)表现出了奇特线型,且MEL的低场(B≤5 mT)和高场(5mT≤B≤500 mT)部分随着掺杂浓度的改变都发生了明显的变化。室温下,随掺杂浓度的改变,MEL低场部分均表现为快速小幅增加。而MEL高场部分的线型和幅度都与掺杂浓度有关：掺杂浓度较大时,MEL随磁场增大先小幅度降低然后大幅增加；掺杂浓度适中时,MEL表现为先增加后降低；掺杂浓度较小时,MEL随磁场单调降低。这种奇特的磁场效应可归结为掺杂体系内超精细相互作用、单重态激子裂变和三重态-三重态激子淬灭三种微观过程共同作用的结果,而不直接产生荧光的三重态激子,可以通过一些自旋混合过程,改变单重态激子的比例,从而对器件发光产生重要影响。器件的工作温度和注入电流密度对磁场效应的影响进一步证实了我们的观点。(3)采用共蒸发技术,制备了结构为ITO/CuPc/NPB/A1q3:Rubrene/BCP/LiF/A1的掺杂型有机发光二极管。测量了不同Rubrene掺杂浓度下掺杂器件的磁场效应。实验发现,器件的MEL表现出复杂变化；在室温下,随着Rubrene掺杂浓度的减小,MEL的线型和幅度都发生了剧烈改变。通过对器件的结构以及材料性质的分析,我们认为在掺杂器件中三重态-三重态激子淬灭(TTA)过程、单重态激子裂变(STT)过程共同存在。因此,本文认为掺杂器件表现出的复杂线型是由于STT和TTA机制共存并相互竞争导致的；随着Rubrene掺杂浓度的减小使得Rubrene分子间的距离增大,STT作用强度减弱,而TTA作用则不受其影响,从磁效应的方面研究了TTA和STT微观机制间的竞争及其微观差异。器件的工作温度和注入电流密度对磁场效应的影响进一步说明在掺杂器件中确实是TTA 和 STT机制共存的,证实了我们上述观点。
[Abstract]:In recent years, in organic optoelectronic devices without any magnetic material (OLEDs) appeared in the peculiar magnetic effect has also aroused people's attention. The mechanism of organic magnetic field effect are researched and put forward many theoretical models. But with the in-depth research, people found that the magnetic effect of OLEDs the complex, yet a micro mechanism can explain all the experimental phenomena. Each mechanism can only partially explain the composition of magnetic effect devices or some specific materials for organic light emitting devices magnetic effect, and for some strange magnetic effect is not very good explanation. Therefore, exploring the microscopic mechanism of complex magnetic effect it has become one of the focus of researchers in this thesis for the first doping type peculiar electric organic light emitting diode emitting magnetic effect and its influencing factors were analyzed by modified. Variable doping concentration, injection current density and temperature change of the magnetic device luminous effect lead to explore microscopic mechanism of the complex magnetic effect. Then, in a singlet exciton fission (STT) and three - three triplet triplet exciton quenching (TTA) properties of doped organic light emitting diode two. Qualitative research on the influence of doping concentration on the doped device magnetic field effect, trying to explore STT and TTA two kinds of micro mechanism between competition and micro difference. This dissertation is mainly divided into the following sections: (1) firstly, introduced the development process of the organic magnetic field effect and its development status: after introduces the research progress of organic the light emitting diode magnetic effect and some physical mechanism of the proposed model, such as the hyperfine interaction model, three - three triplet singlet exciton quenching model, the singlet exciton fission model. In the second chapter of this article mainly introduces the Test method of organic preparation technology and organic magnetic effect of light emitting diode, and some problems in the preparation and the need to pay attention to in the process of testing the device. (2) with fluorescent dye Rubrene singlet and triplet exciton resonance three doped phosphorescent material mCP with high triplet exciton energy in the structure doped organic light emitting diode ITO/CuPc/NPB/mCP:Rubrene/BCP/LiF/A1 was prepared, the magnetic effect of different doping concentration device was measured. MEL. experiments at different concentration device and the measurement of doped El magnetic field effect (MEL) showed a peculiar type, and the low field MEL (B = 5, mT) and the high field (5mT = B = 500, mT) with the doping concentration change have changed obviously. At room temperature, with the doping concentration change, MEL low field showed a rapid increase slightly. While the MEL part of the high field Linear and amplitude are related to the doping concentration: the higher concentration of MEL decreased first, then increased sharply with the increase of magnetic field; doping concentration is moderate, MEL was increased first and then decreased; the doping concentration is MEL hours, with the magnetic field decreases monotonically. This magnetic effect should be attributed to the unique doping system of super fine interaction of singlet exciton fission and three singlet triplet exciton quenching - three interaction of three kinds of micro process results, three singlet exciton without direct fluorescence, through some spin mixing process, change the singlet exciton ratio, which has an important effect on the luminescence device. The working temperature and the injection effect of current density on the magnetic field effect further confirms our view. (3) by CO evaporation technique, were fabricated with the structure of ITO/CuPc/NPB/A1q3:Rubrene/BCP/LiF/A1 doped organic light emitting Magnetic field effect devices. The diode doped with different Rubrene concentration were measured. The experimental results showed that, the MEL device showed complex changes; at room temperature, with the decrease of Rubrene concentration, and the linear range of MEL have undergone dramatic changes. The structure of the device and analysis of material properties, we believe that in doped devices in three - three triplet triplet exciton quenching (TTA) process, the singlet exciton fission (STT) process are common. Therefore, the linear complexity of doped device performance is due to the STT and TTA coexistence and mutual competition mechanism caused; with decreasing concentration of Rubrene Rubrene makes the distance between molecules increase, weakening the strength of STT, while the TTA effect is not affected, from the magnetic effect of TTA was studied and the mechanism of STT competition and micro devices. Differences of temperature and injection current density The effect of the magnetic field on the effect of the magnetic field is further explained by the coexistence of TTA and STT mechanisms in the doped devices, which confirms our view.

【学位授予单位】：西南大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TN383.1

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