【作者】 张淑平；

【导师】 杨延强；

【作者基本信息】 哈尔滨工业大学 ， 光学， 2008， 博士

【摘要】 近年来,有机电致发光器件(organic light-emitting diodes,OLED)方面的研究在世界范围内迅速展开,已经成为平板显示、照明等领域中的研究热点。为了克服目前有机电致发光器件效率低、寿命短的问题,许多新型的有机电致发光材料和器件不断涌现出来。然而人们对这些器件发光的各种过程的基本理解仍然是远远不够的。本论文就是以混合层有机电致发光器件以及量子点-有机混合电致发光器件的应用为背景,研究了混合电致发光材料的电输运以及不同材料之间的能量转移特性。采用飞行时间法(time-of-flight,TOF)研究样品的载流子输运机制,搭建了TOF测试系统。首先利用单层发光材料为研究对象,优化了实验条件,并提出了如何选择取样电阻的方法。除此之外,利用多种电化学手段,对聚[2-甲氧基-5-(2′-乙烯基-己氧基)聚对苯乙烯撑] (MEH-PPV)的单层OLED的载流子注入和传输机制进行了分析。分别以电子传输材料8-羟基喹啉铝(Alq3)、共轭聚合物MEH-PPV、以及非共轭聚合物聚乙烯咔唑(PVK)为研究对象,首先,研究了混合材料之间的能量转移特性。根据F?rster理论计算出F?rster能量转移临界半径,并分别利用不同方法估算出混合体系中的能量转移效率。并通过光致以及电致发光性质,讨论了能量转移对混合层器件性能的影响。其次,采用TOF方法研究了混合薄膜的输运机制。数据分析表明通过改变空穴和电子传输材料的相对浓度,可以得到空穴和电子迁移率相等的混合材料。对有机小分子Alq3和三元合金量子点CdSeS的混合薄膜的能量以及电荷转移机制进行了研究。实验发现,在530 nm激发光下,量子点的平均荧光寿命明显短于纯CdSeS量子点,并且,随着Alq3含量的增加迅速变短。然而在400 nm的激发光下,量子点的荧光寿命随着量子点浓度的增加先增大后减小。最大寿命大约位于量子点浓度为53 wt%的位置处。通过研究证明了产生这种现象的原因是Alq3和CdSeS量子点之间同时存在着F?rster能量转移和光致电荷转移,并且形成相互竞争机制。这些结果预示了可以通过调节和控制能量和电荷转移相互作用改变混合薄膜的发光性能。而对于Alq3和CdTeS/ZnS量子点的研究结果表明由于ZnS壳层的存在限制了它们之间的电荷转移相互作用,因此只存在F?rster能量转移相互作用。研究了Alq3和CdSeS量子点掺杂体系的载流子输运的动力学特性。讨论了掺杂体系的电子迁移的性质,着重研究了掺杂浓度以及电场强度对体系迁移率的影响。实验发现CdSeS量子点的掺杂会引起Alq3样品位置无序的增加,使得样品的载流子迁移率的大小随外加电场强度的增加而减小,而且,这种无序程度会随量子点浓度的变化而改变。同时,Alq3和CdSeS量子点界面之间的电荷转移作用,也会改变样品的载流子迁移率。更多还原

【Abstract】 Research in organic light-emitting diodes (OLED) has been rapidly spread worldwide in recent years. It has become particularly interesting in the fields of flat-panel displays and lighting. In order to overcome the shortcomings of low efficiency, short lifetime, many new kinds of OLED are constantly emerging. However, it’s still far from enough to research the luminescent process of these devices. In this dissertation, we investigate the electronic transport of the blend film and the energy transfer characteristic between different materials, based on the application of blend-layer and quantum dots-organic light-emitting diodes.In order to explore on the characteristic of carrier transport in organics light-emitting materials, we built the setup of time-of-flight (TOF) to measure the charge carrier mobility. We have optimized the requirements at first using monolayer material, and provided a method of selecting the sampling resistor. Besides, we have analyzed the carrier injection and transport properties of monolayer OLED of poly[2-methoxy 5-(2-ethylhexyloxy)-p-phenylene vinylene] MEH-PPV by various electrochemistry methods.Firstly, we investigate the energy transfer process of the blend films of electron transport materials Alq3 and hole transport materials MEH-PPV or PVK. The F?rster radius and the energy transfer efficiency are calculated. Moreover, we investigate the effect of energy transfer on the performance of device by both the PL and EL spectroscopy. Secondly, TOF technique is used to investigate the transport property of blend film. The result exhibits that the blend materials with equivalent mobility of hole and electron can be obtained by adjusting the concentration of the component.In this thesis, we report studies of the energy and charge transfer of the CdSeS QDs (Quantum dots) and organic small molecule material Alq3. With excitation at 530 nm, the fluorescence lifetimes in the blend films show faster decay than pristine CdSeS QDs and decreases with the concentration of Alq3 increasing. However, with excitation at 400 nm, the fluorescence lifetime of CdSeS QDs in blend films are dependent on the concentration, increasing at first and then decreasing as the CdSeS QDs concentration. The maximum lifetime is located at about 53 wt% CdSeS QDs concentration. The reason is that F?rster energy transfer from the Alq3 to CdSeS QDs exists simultaneously with the charge transfer and both compete with each other. These results foreshow that the emission of CdSeS QDs in the blend films can be adjusted by controlling and balancing the energy and charge transfer processes between Alq3 and CdSeS QDs. However, there is only energy transfer process between Alq3 and CdTeS/ZnS QDs, due to the presence of ZnS shell.In order to explore on the dynamics characteristic of carrier transport in the blend films of Alq3 and QDs, we measure the carrier mobility and the dependence on electric filed and QDs concentration. These results show that the positional disorder in the blend films will be increased with the increase of QDs concentration. Moreover, the charge transfer mechanisms between Alq3 and QDs will lead to the change of the charge carrier mobility.更多还原