外场对共轭高分子凝聚态结构的影响

发布时间：2018-05-28 01:04

本文选题：高分子凝聚态结构 + 有序　；参考：《吉林大学》2017年硕士论文

【摘要】：共轭高分子由于具有良好的成膜性、可以实现大面积、加工成本较低,广泛应用在有机太阳能电池,有机发光二极管和有机场效应晶体管领域。共轭高分子的光电理论知识已日渐成熟,其实际应用价值也非常巨大。提高载流子迁移率进而提高器件效率是众多研究者努力的目标。提高高分子材料的有序聚集,并且使其形成互穿网络结构,可以大幅度提高材料的载流子迁移率。高分子材料具有软物质特性,对外场刺激响应强烈。高分子性能不完全取决于化学结构,不同凝聚态结构显示不同的性质。本论文旨在研究外场(溶剂,浓度,转速,温度,电场)对共轭高分子凝聚态结构的影响。进而通过外场调控共轭高分子的有序凝聚态结构达到提高载流子迁移率,最终提高器件效率的目的。高分子前体溶液中分子链的构象和聚集状态以及成膜过程会影响形成薄膜的凝聚态结构,最终影响器件性能。通过系统的研究浓度,旋涂转速,温度和溶剂对PTB7薄膜凝聚态结构的影响,发现:随浓度降低(低缠结度)转速增加(解缠结),PTB7主链共轭长度增加,π-π相互作用增强,有序聚集尺寸增大,主要是由链内相互作用诱导有序聚集,分子链缠结不利于有序聚集,降低有序度;不良溶剂1,2二氯乙烷使PTB7主链缠结,卷曲,而形成无定型态。当继续降低溶剂的溶解性,分子链间吸引力增强,链段间的距离减小,部分链段间π-π相互作用增强,产生局部有序聚集,增加主链共轭长度。我们得出结论:PTB7主要存在3种聚集态结构:1、由分子链内相互作用驱使分子链自折叠形成的有序聚集;2、分子链间缠结形成的无定型态;3、分子链缠结密度达到一定时,部分链段间π-π相互作用增强,产生局部有序聚集。由于高分子具有分子量和分子尺寸的多分散性和物质结构多层次性的特点,PTB7的三种聚集态结构在成膜过程中可能同时存在。结合已有文献报道,我们推测增加分子链自折叠形成的小尺寸有序聚集,减少分子链缠结形成的无定型态,可以提高载流子迁移率,达到提高器件效率的目的。这对提高光电器件效率具有重要的理论与实际意义。电场对共轭高分子凝聚态结构影响的研究非常少,但是具有方向性的电场对共轭高分子链取向的作用不容忽视。我们通过在玻璃化转变温度以上退火的过程中加电场,研究电场对不同极性高分子链取向的影响,发现:电场增强P3HT主链π-π相互作用,并且增大其结晶度;电场使MEH-PPV主链共轭长度有微弱增加,并使其聚集减少。得出结论:P3HT主链S原子具有较强的电负性,偶极矩较大,在电场作用下响应更加明显。MEH-PPV虽然含有两个电负性较强的O原子,但由于其处在对称位置上,所以整体偶极矩较小,在电场作用下响应微弱。极性高分子在电场作用下,有序度增加。并且偶极矩(极性)越大,电场对其调控作用越显著。
[Abstract]:Conjugated polymers are widely used in the fields of organic solar cells, organic light emitting diodes and field effect transistors due to their good film-forming properties, large area and low processing cost. The photoelectric theory of conjugated polymer has matured and its practical application value is very great. Increasing carrier mobility and thus improving device efficiency is the goal of many researchers. The carrier mobility can be greatly improved by increasing the ordered aggregation of polymer materials and forming an interpenetrating network structure. The polymer material has the soft matter characteristic, the external field stimulates the response to be strong. The properties of polymer are not completely dependent on the chemical structure, and different condensed matter structures show different properties. In this paper, the effects of external field (solvent, concentration, rotation speed, temperature, electric field) on the condensed structure of conjugated polymers are studied. Furthermore, the ordered condensed matter structure of conjugated polymer is controlled by external field to improve the carrier mobility and the device efficiency. The conformation and aggregation of molecular chains in polymer precursor solution and the process of film formation will affect the condensed structure of the film and ultimately affect the performance of the device. The effects of concentration, spin-coating speed, temperature and solvent on the condensed structure of PTB7 thin films were systematically studied. It was found that the 蟺-蟺 interaction increased with the decrease of concentration (low entanglement degree) and the increase of conjugation length of the main chain of PTB7. The ordered aggregation size is increased, which is mainly induced by intrachain interaction, the molecular chain entanglement is not conducive to the ordered aggregation, and the order degree is reduced, and the bad solvent 1 ~ (2) dichloroethane makes the PTB7 main chain entangled, curled, and forms an amorphous state. When the solubility of the solvent continues to decrease, the attraction between chains increases, the distance between segments decreases, and the 蟺-蟺 interaction between some segments increases, resulting in a local ordered aggregation and an increase in the conjugate length of the main chain. We draw the conclusion that there are three kinds of aggregation structure: 1, the ordered aggregation of molecular chains driven by intra-chain interaction, the formation of interchain entanglement, and the formation of interchain entanglement, when the molecular chain entanglement density reaches a certain degree. The 蟺-蟺 interaction between partial segments is enhanced, resulting in local ordered aggregation. Due to the polydispersity of molecular weight and molecular size and the multilevel structure of PTB7, the three aggregates of PTB7 may exist simultaneously in the process of film formation. Combined with the previous reports, we speculate that increasing the small size ordered aggregation of molecular chain self-folding and reducing the amorphous state formed by molecular chain entanglement can increase the carrier mobility and achieve the purpose of improving the device efficiency. It is of great theoretical and practical significance to improve the efficiency of optoelectronic devices. The effect of electric field on conjugated polymer structure is very little, but the effect of directional electric field on the orientation of conjugated polymer chain can not be ignored. We study the effect of electric field on the orientation of different polarity polymer chains by adding electric field in the process of annealing above glass transition temperature. It is found that the electric field enhances the 蟺-蟺 interaction of the main chain of P3HT and increases its crystallinity. The electric field increases the conjugate length of the main chain of MEH-PPV slightly and reduces its aggregation. It is concluded that the S atom of the W P3HT main chain has strong electronegativity, larger dipole moment, and more obvious response under electric field. Although there are two O atoms with strong electronegativity, the whole dipole moment is smaller because of its symmetrical position. The response is weak under the action of electric field. The order of polar polymer increases under the action of electric field. The greater the dipole moment (polarity) is, the more significant the electric field is.
【学位授予单位】：吉林大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O631.1

【相似文献】