【作者】 王经；

【导师】 何谷峰；

【作者基本信息】 上海交通大学 ， 电子科学与技术， 2014， 硕士

【摘要】 掺杂是在有机发光二极管（OLED）中被广泛应用的一种技术。将发光材料掺杂在适当的发光层主体材料中，可使电致发光的量子效率得到大幅提升；而将p型或n型掺杂剂分别掺杂在对应的空穴或电子传输层的主体材料中，可以显著提高载流子的注入与传输特性，改善器件的功率效率。通常，在这两种应用掺杂技术的有机层中，所使用的材料都是互相均匀掺杂的，但这种均匀掺杂技术仍然存在一定缺陷。本文旨在研究一种新型的渐变掺杂技术，将其引入有机发光二极管器件结构设计中以弥补均匀掺杂的不足，进而提高器件性能。围绕这一课题，本文展开了如下工作：渐变掺杂技术在发光层中的应用本文首先设计了一种简化结构的磷光有机发光二极管，利用常用蓝光发光主体材料同时作为发光层和传输层，不仅降低了工艺复杂度和材料成本，还有效地减少了因载流子在发光区域附近累积所造成的激子淬灭效应。基于这一简化有机发光二极管的器件设计方法，本文研究了渐变掺杂技术在发光层中的应用。渐变掺杂主体结构是在保证发光材料掺杂浓度不变的前提下，将两种主体材料的浓度分别由高到低和由低到高，线性渐变共混的结构。相比较于传统的双发光层和混合主体结构而言，渐变掺杂主体结构可以显著拓宽载流子复合区域，从而提高器件效率，降低效率滚降。为了简化器件的制备，本文进一步提出一种梯度掺杂以拟合渐变掺杂的浓度变化。经过优化，采用梯度掺杂主体结构的器件在亮度为1000cd/m2和10,000cd/m2时外量子效率分别高达21.0%和19.3%，效率滚降仅为8.0%。渐变掺杂技术在传输层中的应用本文首次提出了一种新型的非线性渐变掺杂技术。在传输层的渐变掺杂掺杂中，靠近电极处的高浓度掺杂可以有效提高载流子的注入性能，而靠近发光层处的低浓度掺杂不仅可以保证载流子具有较高的迁移率，同时可以还防止掺杂剂的扩散。同时，中间区域的渐变掺杂可以为载流子提供平滑的传输通道。通过实验可以证明，在空穴传输层和电子传输分别采用渐变掺杂均可以显著提高器件的电流特性和功率效率。更多还原

【Abstract】 Doping technology has been widely used in organic light-emittingdiodes (OLEDs). Doping emitters with a suitable concentration in matrixcan increase the quantum efficiency of electroluminescence significantly,while introducing p-tpye and n-type dopant into hole and electrontransporting layer, respectively, will boost the charge carrier injection andtransport, and improve the power efficiency of OLEDs. Normally, thedopant is uniformly doped in the matrix in such system. However, theuniform doping method still has some drawbacks. The thesis aims atstudying a new crossfading doping method in the design of OLED devicesto overcome the disadvantages of uniform doping and enhance deviceperformance. Focusing on the topic, the thesis is organized as following:Crossfading doping in light-emitting layerAs the first step, we have designed a simplified phosphorescentorganic light-emitting diode by using a common blue matrix material asboth light emitting layer (EML) and transporting layer. The simplified structure not only reduces the process complexity and the material cost, butalso decreases the exciton quenching caused by carrier accumulation nearthe recombination zone. Based on the simplified structure, we have studiedthe application of the crossfading doping in EML. The crossfading-hoststructure is to mix two matrix materials in a crossfading profile, ensuringthe doping concentration of the emitter is stable. Compared withconventional double emission and co-host structure, crossfading-hostbroadens the recombination zone distinctly, and further enhances deviceefficiency and reduces roll-off. We also introduce a gradient doping to fitthe doping profile of crossfading doping to simplify the process. Afteroptimizations, a device with gradient doping achieves external quantumefficiency of21.0%and19.3%at the luminance of1000cd/m2and10,000cd/m2, respectively. The efficiency roll-off is only8.0%.Crossfading doping in transporting layersWe have proposed a novel nonlinear crossfading doping technology intransporting layers for the first time. In the crossfading doping intransporting layers, the high doping concentration near electrodesimproves the efficiency of carrier injection, and the low dopingconcentration near EML prevents the dopant diffusion into EML.Meanwhile, intermediate region doping provides a smooth transport path for carriers as well. We have proved that crossfading doping in hole andelectron transporting layer can significantly increase the I-V characteristicsand power efficiency of OLED devices.更多还原