盘状分子的取向、光电性能及其器件应用的初步探索

发布时间：2018-05-12 17:56

本文选题：盘状分子 + 盘状液晶　；参考：《北京交通大学》2017年博士论文

【摘要】：大环盘状液晶分子材料多由较大的芳香中心核组成,并具有一定的自组装和分子取向倾向,获得分子取向的盘状液晶材料,往往具有优异的光电物理特性,其高度各向异性的结构可使其在一定方向上的性能得以优化,从而获得高的载流子迁移率、长的激子扩散长度。尤其是其结构缺陷的自我修复能力,可使得其优异的性能保持高度的稳定性,令人瞩目。因而被认为是极具潜力的、新一代的有机光电子材料。本论文围绕一系列新型盘状液晶有机材料在光电子器件中的应用,特别是太阳能电池领域的应用,展开了一系列的基础研究,具体研究内容包括如下几个方面:1.本论文首先研究了如何采用盘状液晶材料,制备具有垂面(homeotropic or face-on)分子取向的薄膜。鉴于常规盘状液晶垂面分子取向结构的获得均采用将盘状液晶材料灌注入标准液晶盒的方式,但是此方法显然不适用于逐层构造的光电子器件的制作。本论文将探索在单一基片表面制备可应用的大面积分子垂面取向的方法。虽然在液晶盒中获得垂面分子取向的报道很多,迄今为止,能在单一基片表面上获得面积垂面分子取向的材料却寥寥无几,这为其在光电子器件中的应用带了巨大的挑战。本论文结合偏光显微镜和X射线衍射实验技术,研究了一系列盘状液晶材料的分子取向。重点研究了具有电双极性的盘状液晶苯并菲SK-75和电子传输性能的蒽醌类盘状液晶AQ6两种新材料的分子取向特性。本研究第一次尝试通过温度调控的方法,实现了 SK-75和AQ6在单一衬底表面上的大面积、稳定、均匀、六方对称高度有序的垂面分子取向,并测得其结构参数。对比H4TP、H5TP、TPT-BAE较为熟悉的盘状液晶材料的分子取向发现,分子结构,尤其是柔性侧链的结构是影响苯并菲类盘状液晶材料取向的关键因素,同时还需选择适当的温控条件,才能获得较好的分子取向。本研究还在上述温度调控垂面分子取向的基础上上,进一步引入掺杂诱导辅助的方法研究取向效果。实现了给受体复合体系oo-CuPc:AQ6以及同质复合体系H4TP:SK-75的诱导分子取向调控。2.以苯并菲TPT-BAE和蒽醌AQ6盘状液晶材料为代表,研究了分子取向对光物理特性及载流子迁移率的影响。木论文创新性的采用与实际有机光电子器件制备方法一致的逐层生长法,通过温度调控在衬底表面上实现了苯并菲TPT-BAE及蒽醌AQ6盘状分子垂面取向,构建了接近实际应用的器件结构,并分别对两种分子取向薄膜的光电性能展开了研究,最后展开了初步光伏器件制备的尝试。研究发现,短波长的吸收光谱与盘状分子的取向密切相关。分子垂面取向后,TPT-BAE及蒽醌AQ6在短波段的紫外吸收显著增强;TPT-BAE薄膜材料呈双极性载流子(空穴和电子)迁移,垂面取向使得薄膜的空穴和电子迁移率均获得近三个数量级的提高,分别达到6.25×10-2和4.28×10-2cm2V-1s-1,接近目前已知的苯并菲类盘状液晶双极性载流子迁移率的最大值。这是首次尝试采用飞行时间法研究在单一衬底上垂面取向生长的盘状液晶的载流子传输特性。率先报道了具有分子取向的新型蒽醌类盘状液晶材料的电子传输特性。采用逐层生长法,构建了基于蒽醌AQ6在单一衬底上生长的垂面分子取向薄膜,研究发现,分子取向的蒽醌AQ6薄膜在紫外短波段光吸收显著增强,有效地提高了吸收截面;通过构造唯电子器件,并用空间电荷限制电流(SCLC)方法研究薄膜的载流子迁移率,分子取向后的电子迁移率可提高两个数量级,达到1.2×10-2 cm2V-1-s-1。采用在单一基片上生长的垂面取向结构研究电子传输盘状液晶的载流子传输特性,在国际上尚属首例。3.采用n型蒽醌AQ6盘状液晶为受体材料,研究了其与给体聚合物制备本体异质结太阳能电池的可行性。研究首次尝试将蒽醌AQ6分别与p型给体材料MEH-PPV、P3HT共混,制备了相应的本体异质结太阳能电池器件,探索将AQ6作为受体材料应用于聚合物太阳能电池的可行性。研究发现,AQ6与MEH-PPV之间由于存在分子间相互作用,不能有效地产生光伏响应,推测发生了分子间电荷转移,使得该组合不能成为有效的给受体组合;而AQ6与P3HT之间的相互作用较小,该组合可以产生光伏输出,这说明蒽醌类盘状液晶材料可以作为受体应用于有机聚合物本体异质结太阳能电池器件中。4.以盘状大分子金属酞菁作为有机层与非晶硅杂化的结构非晶硅与有机材料的复合或杂化结构的研究极其稀少,本论文第一次创新性地采用非晶硅与盘状大分子金属酞菁的简单复合结构,并制备了太阳能电池,研究该结构的光伏响应特性。研究发现,非晶硅/金属酞菁可以获得光伏输出,器件的光伏性能与金属酞菁层的厚度密切相关;光电流的贡献主要来自于非晶硅层。分析表明,金属酞菁层与非晶硅层之间不平衡的载流子传输能力限制了载流子的传输和收集效率,这为以后杂化器件的结构和性能优化提供了新的方向。全文共图53幅,表8个,参考文献277篇。
[Abstract]:The macrocyclic liquid crystal molecular material is composed of large aromatic core nuclei, and has a certain tendency of self-assembly and molecular orientation. The molecular oriented disk liquid crystal materials often have excellent photoelectric physical properties. The highly anisotropic structure can optimize the performance of a certain square up and thus obtain high load current. The migration rate, the long exciton diffusion length, especially the self repair ability of its structural defects can make its excellent performance maintain high stability and attract people's attention. Therefore, it is considered as a potential new generation of organic optoelectronic materials. This paper focuses on a series of new discoid liquid crystal organic materials in optoelectronic devices. A series of basic studies have been carried out, especially in the field of solar cells. The specific research contents include the following aspects: 1. this paper first studied how to use disk like liquid crystal materials to prepare thin films with homeotropic or face-on molecular orientation. This method is obviously not suitable for the fabrication of optoelectronic devices with layer by layer structure. This paper will explore the method for the preparation of large area molecular vertical orientation on the surface of a single substrate. Although there are many reports on the orientation of the vertical surface in the liquid crystal box, we have so far So far, few materials can be obtained on the surface of a single substrate. This is a great challenge for its application in optoelectronic devices. In this paper, the molecular orientation of a series of disk like liquid crystal materials is studied by polarizing microscope and X ray diffraction technique. The molecular orientation properties of two new materials, discoid benzo phenanthrene SK-75 and electron transport properties of anthraquinone discoid liquid crystal AQ6. The first attempt to achieve a large area, stable, uniform, six square symmetrical and highly ordered vertical surface molecular orientation on the surface of a single substrate by the method of temperature regulation, and the structure of SK-75 and AQ6 The molecular orientation of the H4TP, H5TP, and TPT-BAE discoid liquid crystals is found to be the key factor affecting the orientation of the phenanthrene discoid liquid crystal material, especially the structure of the flexible side chain, and a suitable temperature control condition is needed to obtain better molecular orientation. On the basis of surface molecular orientation, the effect of orientation was further introduced by doping inducement. The induced molecular orientation of oo-CuPc:AQ6 and H4TP:SK-75 in the homogenous complex system was controlled by.2., which was substituted by phenanthrene TPT-BAE and anthraquinone AQ6 discoid liquid crystal. The influence of carrier mobility. The paper innovatively adopts the layer by layer growth method consistent with the actual organic optoelectronic device preparation method. Through the temperature regulation, the vertical surface orientation of phenanthrene TPT-BAE and anthraquinone AQ6 disk molecules is realized on the substrate surface, and the device structure close to the actual application is constructed, and two kinds of molecular oriented films are made respectively. It is found that the short wavelength absorption spectrum is closely related to the orientation of the disc molecules. After the vertical plane orientation, the UV absorption of TPT-BAE and anthraquinone AQ6 increases significantly in the short band, and the TPT-BAE thin film materials migrate in the bipolar carrier (hole and electron). The vertical plane orientation makes the cavitation and electron mobility of the thin films increase nearly three orders of magnitude, reaching 6.25 * 10-2 and 4.28 x 10-2cm2V-1s-1 respectively. It is close to the maximum value of the known phenanthrene discoid liquid crystal bipolar carrier mobility. This is the first attempt to study the vertical surface orientation growth on a single substrate by the flight time interval method. The carrier transmission characteristics of the disk like liquid crystal have been reported. The electron transport characteristics of the novel anthraquinone discoid liquid crystal materials with molecular orientation are reported. A layer by layer growth method is used to construct the pendant surface molecular oriented film based on the anthraquinone AQ6 on a single substrate. The study shows that the molecular oriented anthraquinone AQ6 thin film is absorbed in the UV short band light absorption. The absorption cross section is significantly enhanced and the carrier mobility of the film is studied by constructing a electronic only device and using the space charge limited current (SCLC) method. The electron mobility of the molecule can be increased by two orders of magnitude, and the vertical structure of a 1.2 x 10-2 cm2V-1-s-1. which is grown on a single substrate is used to study the electron transfer. The carrier transmission characteristics of disk like liquid crystals are the first example of.3. using N type anthraquinone AQ6 disk liquid crystal as the receptor material. The feasibility of preparing bulk heterojunction solar cells with donor polymers was studied. The first attempt was to blend the anthraquinone AQ6 with the P donor MEH-PPV and P3HT, and the corresponding bulk heterostructure was prepared. A solar cell device is used to explore the feasibility of applying AQ6 as a receptor material to polymer solar cells. It is found that the interaction between AQ6 and MEH-PPV can not produce the photovoltaic response effectively because of the intermolecular interaction. It is presumed that the charge transfer between molecules has occurred, making the combination not an effective donor combination; and AQ6 The interaction between P3HT is smaller and the combination can produce photovoltaic output, which shows that the anthraquinone discoid liquid crystal material can be used as a receptor in the organic polymer bulk heterojunction solar cell devices, and.4. is used as the composite or heterozygous of amorphous silicon and organic materials. The study of chemical structure is very rare. In this paper, the simple composite structure of amorphous silicon and disk macromolecular metal phthalocyanine was first used in this paper. The solar cell was prepared and the photovoltaic response characteristics of the structure were studied. It was found that the photovoltaic output of the amorphous silicon / metal phthalocyanine can be obtained. The photovoltaic performance of the device and the thickness of the metal phthalocyanine layer are also found. The contribution of the optical current mainly comes from the amorphous silicon layer. The analysis shows that the unbalanced carrier transport capacity between the metal phthalocyanine layer and the amorphous silicon layer restricts the transport and collection efficiency of the carrier, which provides a new direction for the structure and performance optimization of the hybrid devices. The full text is 53, 8, and 277 references. Article.

【学位授予单位】：北京交通大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：O753.2

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