有机电光材料的太赫兹关键性能研究

发布时间：2018-05-07 19:48

本文选题：太赫兹频段 + 单组分有机电光材料　；参考：《电子科技大学》2016年博士论文

【摘要】：太赫兹技术在通信、雷达、安检、射电天文、生物医学等多个领域中的重要价值得到当今科学界愈益增加的认可。在这一新兴科学技术领域,太赫兹辐射产生与检测的能力与水平成为推动太赫兹技术发展的关键。利用电光材料的光整流效应产生太赫兹波、电光取样技术检测太赫兹波,是实现宽频带太赫兹波产生和检测的常用方法之一。相比传统的电光晶体材料,有机电光材料具有非线性光学系数大、响应速度快、无声子吸收带隙等优点,并可根据需求进行分子设计、修饰,易于提高材料性能,在太赫兹技术研究中得到了广泛的关注。其中,高数密度单组分有机电光材料以其在电光性能方面的巨大潜力,近年来迅速成为电光材料领域关注的热点。然而,为了使这类材料能够满足太赫兹波产生与检测的应用要求,必须对包括电光活性、热稳定性和吸收损耗等材料关键性能进行进一步的综合优化。本文分析了电场极化引入发色团取向过程中的电导机理,利用固态器件工程概念减少泄漏电流,提高了单组分有机电光材料的电光系数;建立了单组分有机电光材料固有极化效率的评估标准;系统地研究了单组分有机电光发色团的结构性质关系,拓展了分子结构对材料重要性能影响的认知体系;探索研究了有机电光材料在太赫兹频段折射率和吸收系数的快速表征方法。具体研究内容包括:1.苯并环丁烯阻挡层对极化过程中器件电导的抑制研究。单组分有机电光材料由于材料体系中有机电光发色团数密度的增加,大大提高了电光性能,但也因此导致材料电导率的增加,其引发的泄漏电流在极化过程中限制发色团分子的取向,成为实现大的电光系数所面临的主要挑战。本文通过对极化过程中泄漏电流本质的理解和器件电导机理的分析,提出了在电极和电光材料层的交界面引入苯并环丁烯阻挡层,以阻止电荷注入。研究了阻挡层厚度对材料电光活性实现的影响,确定了阻挡层的最优厚度区间。苯并环丁烯阻挡层的使用,有效降低了极化过程中的泄漏电流或器件电导,保持有效极化电压与外加电压近似相等,显著提高了高数密度单组分有机电光材料的电光系数,所观察到的最大电光系数是无阻挡层器件的2倍左右。其中,材料JRD1在极化电场大于85 Vμm-1的条件下,多次测试的电光系数超过之前报道的最大值400 pm V-1,并获得了目前所报道的最大电光系数556 pm V-1。对比实验证明苯并环丁烯阻挡层对泄漏电流的抑制度比目前最常用的二氧化钛阻挡层提高了一至两个数量级。2.单组分有机电光材料极化效率的评估标准研究。单组分有机电光材料的高电导率问题导致极化过程中电场强度的明显降低,之前沿用的以外加电场强度作为极化电场强度的方法不能准确计算此类材料的极化效率。针对这个问题,本文提出用极化过程中的平均电场强度作为极化电场值,通过电压数据的分段拟合进行计算。极化电场的这种修正算法充分考虑了极化过程中电场强度下降对电光系数的影响,使得从传统器件的电光特性表征中就能准确地评估单组分发色团的实际电光性能。3.单组分有机电光发色团的结构性质关系研究。单组分有机电光材料在应用中有两个潜在的不利条件:一是部分单组分有机电光发色团易结晶,发生相位分离;二是这类材料热稳定性(主要反映在玻璃化温度)普遍偏低,降低工作装置的可靠性和寿命。针对这个问题,本文研究了有机电光发色团的结构性质关系,通过对现有分子结构的渐进式改变,探索分子修饰对材料的最大电光系数、极化效率、玻璃化温度和电导率等重要参数的影响。提出采用体积较大的叔丁基二苯基硅烷基团对电子给体进行修饰,以促进非晶态薄膜的形成和极化效率的提高。在此基础上,通过在电子桥上增加咔唑位置隔离基团,有效减小了分子间的偶极-偶极相互作用,制备出的材料极化效率约为3 nm2/V2,是目前报道的最高值,并且玻璃化温度提高到100?C以上,比已见报道的同类材料提高了20-40?C。4.超薄聚合物膜在太赫兹频段的光学特性研究。有机电光材料在太赫兹波产生与检测中的应用需要解决相位匹配和吸收损耗问题,因此在选择材料时,需要知道材料的折射率和吸收系数。传统测试方法要求待测样品厚度较大,存在与厚膜制作加工相关的一系列难题。本文探索性研究了利用衰减全反射技术在有机电光材料超薄薄膜上进行折射率和吸收系数测试的方法,提出了应用于该测试方法的新的器件结构,建立了一种与之相对应的多层结构分析模型,并利用Matlab程序实现了对材料在太赫兹频段折射率和吸收系数的分析。可行性验证实验显示利用该方法测得的材料折射率和吸收系数与传统方法的测试结果有良好的一致性。有机电光材料极化前后的折射率和吸收系数通过在几个微米厚的薄膜上进行测试即可获得,实现了对材料光学特性的快速表征。
[Abstract]:The important value of terahertz technology in many fields, such as communication, radar, security, radio astronomy, biomedicine, and other fields, is gaining recognition. In this new field of science and technology, the ability and level of the generation and detection of terahertz radiation is the key to the development of terahertz technology. The terahertz wave should be produced by the terahertz wave. It is one of the common methods to realize the generation and detection of the broadband terahertz wave. Compared with the traditional electrooptic crystal material, the organic electro-optic material has the advantages of large nonlinear optical coefficient, fast response speed, no sound absorption band gap and so on, and can be designed and modified according to the demand. In the study of terahertz technology, the high density of single component organic electro-optic materials have become a hot spot in the field of electrooptic materials in recent years. However, in order to make this kind of materials meet the application of terahertz generation and detection It is required to further optimize the key properties of materials including electrooptic activity, thermal stability and absorption loss. This paper analyzes the conductivity mechanism of the electric field polarization introduced into the chromophore orientation process, reduces the leakage current by using the concept of solid-state device engineering and improves the electrooptic coefficient of the single component organic electrooptic material. The evaluation criteria for the intrinsic polarization efficiency of the single component organic electro-optic materials, the structural properties of the single component organic electrooptic chromophore, the cognitive system of the influence of the molecular structure on the material properties, and the rapid characterization of the emissivity and absorption coefficient of the organic electrooptic materials in the terahertz band are explored and studied. The study includes: the study of the inhibition of the conductance of the device in the polarization process of 1. benzo - butylene barrier. Single component organic electrooptic material increases the electrooptic performance greatly because of the increase of the number density of the organic light chromophore in the material system, but it also leads to the increase of the conductivity of the material, and the leakage current caused by the single component is limited in the polarization process. The orientation of the chromophore has become a major challenge for the realization of large electro-optical coefficients. By understanding the nature of the leakage current in the polarization process and the analysis of the mechanism of the device conductance, a benzo butylene barrier is introduced into the interface of the electrode and the electrooptic material layer to prevent the charge injection. The optimal thickness of the barrier layer is determined by the effect of the electrooptic activity. The use of the benzo butylene barrier effectively reduces the leakage current or the device conductance in the polarization process. The effective polarization voltage is approximately equal to the applied voltage, and the electro-optical coefficient of the high density single component organic electro-optic material is greatly improved. The maximum electro-optical coefficient is about 2 times that of the non barrier device. In the condition of the polarization electric field greater than 85 V M-1, the electrooptic coefficient of multiple tests is higher than the maximum value of the previously reported 400 PM V-1, and the maximum electro-optical coefficient of the present reported 556 PM V-1. has been reported to prove the leakage of the benzo butylene barrier over the experiment. The inhibition of current is higher than the most commonly used titanium dioxide barrier layer, which improves the evaluation standard of the polarization efficiency of one to two orders of magnitude.2. single component organic light materials. The high conductivity of the single component organic electro-optic material leads to the obvious decrease of the electric field intensity in the polarization process, and the electric field intensity as the polarization used before is used as the polarization. The method of electric field strength can not accurately calculate the polarization efficiency of this kind of material. In this paper, the average electric field intensity in the polarization process is used as the polarization field value and the piecewise fitting of the voltage data is calculated. This correction algorithm of the polarization field fully considers the electric field intensity decrease to the electro-optic system in the polarization process. The influence of the number makes it possible to accurately evaluate the actual electro-optic properties of single group distribution chromophores from the electrooptic characterization of traditional devices. The structural properties of.3. monocomponent organic light chromophores are studied. There are two potential adverse conditions in the application of single component organic electro-optic materials: one is that some monocomponent organic light chromophores are easy to knot. Crystal, phase separation, two is the thermal stability of this kind of material (mainly reflected at the glass temperature) is generally low, reducing the reliability and life of the working device. In this paper, the structure and property relationship of the organic electrooptic chromophore is studied. By the gradual change of the existing molecular structure, the maximum of the molecular modification to the material is explored. The effect of electrooptic coefficient, polarization efficiency, vitrification temperature and electrical conductivity, and so on. A large volume tert butyl two phenyl silane group was used to modify the electron donor in order to promote the formation of amorphous film and increase the polarization efficiency. On this basis, the effect of carbazole position isolation group was increased by increasing the position of carbazole. When the dipole dipole interaction between molecules is small, the polarization efficiency of the prepared material is about 3 nm2/V2, which is the highest value reported at present, and the glass temperature increases to more than 100? C. The optical properties of the 20-40? C.4. ultra-thin polymer film in the terahertz band are improved compared with the similar materials that have been reported. The organic electro-optic materials are in the terahertz wave. The application of generation and detection needs to solve the problem of phase matching and absorption loss, so it is necessary to know the refractive index and absorption coefficient of the material in the selection of materials. The traditional testing method requires that the thickness of the sample is large and there is a series of problems related to the fabrication and processing of thick film. The method of measuring the refractive index and absorption coefficient on the ultra-thin film of the organic electrooptic material is carried out. A new device structure applied to the test method is proposed. A multi-layer structure analysis model corresponding to it is established. The analysis of the refractive index and absorption coefficient of the material in the terahertz band is realized by the Matlab program. The experimental results show that the refractive index and absorption coefficient of the material obtained by this method are in good agreement with the test results of the traditional method. The refractive index and absorption coefficient of the organic electrooptic material before and after polarization can be obtained by testing on a few micron thick films, and the rapid characterization of the optical properties of the material is realized.

【学位授予单位】：电子科技大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TN204

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