有机太阳电池光生载流子动力学过程的瞬态光电导以及瞬态光致吸收光谱研究

发布时间：2018-04-22 09:24

本文选题：有机本体异质结太阳电池 + 亚纳秒级瞬态光电导　；参考：《华南理工大学》2014年博士论文

【摘要】：有机太阳电池是目前太阳能研究领域的热点研究方向。相比起已发展成熟的无机半导体太阳电池技术，有机太阳电池有一些独特的优点，但是效率偏低,是限制其大规模应用的主要因素。为了让有机太阳电池成为真正能实际大规模应用推广的产品，必须进一步提高其能量转换效率，而为了做到这一点，必须深入了解有机太阳电池的工作机理。太阳电池的工作机理最重要的问题取决于三个物理过程：光生载流子的产生、光生载流子的复合以及光生载流子的输运。以上三个过程的时间尺度在数百飞秒到数纳秒的范畴，本论文的研究目的在于运用各种快速响应实验技术探明有机太阳电池材料在这些时间尺度上的超快速光生载流子动力学过程。本论文的研究主要通过亚纳秒级瞬态光电导测量技术以及飞秒级瞬态光致吸收光谱测量技术这两种实验手段，对小分子体异质结太阳电池以及聚合物体异质结太阳电池两类高效率有机太阳电池材料体系的载流子生成，复合以及输运三方面问题进行详细研究。除此之外，本论文还涉及新型负电极修饰层的研究以及其在有机光致发光器件以及有机太阳电池器件中的应用。本论文分为五大部分。第一部分研究通过亚纳秒级瞬态光电导实验测量了两种使用小分子给体的高效率体异质结材料体系的瞬态光电导特性及其在不同温度的表现。研究发现小分子体异质结薄膜的无序程度与聚合物体异质结薄膜相差不大，但是载流子输运可以更长时间保持高迁移率的自由输运，，对有机太阳电池的效率提高有利。另外发现小分子材料体系与聚合物材料体系的载流子在陷阱能级中的弛豫过程完全不同，小分子材料体系的载流子迁移率衰减明显慢于聚合物材料体系，这一特性有可能对小分子有机太阳电池器件的高效率有积极贡献。第二部分进一步研究有机太阳电池材料体系的超快速电荷分离过程，通过飞秒级瞬态光致吸收光谱实验方法考察了一种高效可溶液加工小分子给体材料的体异质结薄膜以及双层结构薄膜的光生载流子动力学特性。本部分研究结果进一步验证了超快速电荷分离模型的正确性，并表明超快速电荷分离过程产生的根本原因是有机半导体材料激发态的波函数在数百飞秒的时间尺度内是量子相干叠加的，本征具有离域性。本部分研究提出了提高有机太阳电池性能的新思路，即延长有机太阳电池材料的量子退相干时间。第三部分工作改进了飞秒级瞬态光致吸收光谱测量系统用以测量瞬态光致反射光谱，并考察了五种高效有机太阳电池体异质结材料体系的实际太阳电池器件的瞬态光致反射光谱，从中获得了实际器件中的载流子动力学过程以及这一过程与电场强度的相关性。研究发现这些高效材料体系中不存在明显的孪生对复合现象。另外本部分研究结果表明超快电荷分离过程的确存在于实际太阳电池器件中，且器件样品中的载流子生成过程与薄膜样品类似。第四部分工作将两种新型非离子型可交联水/醇溶聚合物作为单独负电极修饰层材料应用于倒装有机电致发光器件中。发现使用新型负电极修饰层材料的倒装有机电致发光器件的效率非常高，可以和最好的普通结构器件相媲美，从而证明了非离子型可交联水/醇溶聚合物作为负电极修饰层的巨大价值，值得将其推广到有机太阳电池应用领。第五部分工作系统研究了五种不同离子型的水/醇溶共轭聚合物作为聚合物太阳电池的负电极修饰层的性能。研究发现全部材料都能不同程度提高普通结构以及倒装结构聚合物太阳点器件的性能，其中以两性离子型材料以及非离子型材料在普通结构器件中性能最佳，自由阴离子型材料在倒装结构器件中表现最佳，而自由阳离子型材料在倒装结构器件中反而降低器件性能。我们从两个理论模型出发考察水/醇溶共轭聚合物材料作为负电极修饰层的机理：离子重新分布理论以及界面电偶极子理论。最终证明两方面都对水/醇溶共轭聚合物材料作为负电极修饰层的性能有贡献，而且自由阴离子型水/醇溶共轭聚合物理论上最适合作为负电极修饰层材料。
[Abstract]:Organic solar cells are the hot research fields in the field of solar energy research. Compared with the mature inorganic semiconductor solar cell technology, organic solar cells have some unique advantages, but the efficiency is low, which is the main factor limiting the large-scale application of the solar cells. In order to make the solar cells of the machine truly practical and large-scale application In order to achieve this, we must further understand the working mechanism of the organic solar cell. The most important problem of the working mechanism of the solar cell depends on three physical processes: the generation of the optical carrier, the recombination of the photogenerated carrier, and the transport of the light carrier.
The time scale of the above three processes is in the range of hundreds of femtosecond to nanosecond. The purpose of this paper is to explore the ultra fast optical carrier dynamics process of organic solar cell materials on these time scales by using various fast response experiments. In addition to the two experimental methods, such as the carrier generation, recombination and transport of two kinds of high efficiency organic solar cell materials, such as small molecular body heterojunction solar cells and two kinds of polymer heterojunction solar cells, the two experimental means are also studied in detail. The new negative electrode modified layer and its application in organic light emitting devices and organic solar cell devices are divided into five parts.
In the first part, the transient photoconductivity of two high efficiency bulk heterojunction materials using small molecule donor and its performance at different temperatures were measured by the subnanosecond transient photoconductivity test. It is beneficial to improve the efficiency of organic solar cells for the free transport of high mobility for longer time. In addition, it is found that the relaxation process of the carrier in the trap level of the small molecular material system and the polymer material system is completely different, and the decay of the carrier migration rate of the small molecular material system is obviously slower than that of the polymer material system. One characteristic may contribute positively to the efficiency of small molecule organic solar cell devices.
In the second part, the ultra fast charge separation process of the organic solar cell material system is further studied. By the femtosecond transient photoinduced absorption spectroscopy, a high efficiency solution processing small molecular donor body heterojunction film and the photodynamic characteristic of the two-layer structure film are investigated. One step is to verify the correctness of the ultra fast charge separation model and show that the fundamental reason for the ultra fast charge separation process is that the wave function of the excited state of the organic semiconductor material is superposed by quantum coherency in the time scale of hundreds of femtosecond, and the eigenvalue is off domain. This part of the study proposes a new method to improve the performance of organic solar cells. The idea is to extend the quantum decoherence time of organic solar cell materials.
The third part has improved the femtosecond transient photoinduced absorption spectrum measurement system to measure transient photoinduced reflectance spectroscopy, and investigated the transient photoinduced reflectance spectra of the actual solar cell devices of five kinds of high efficient organic solar cell heterojunction materials. The relationship between the process and the strength of the electric field has been found. It is found that there are no obvious twin pairs in these high efficiency materials. In addition, the results show that the ultrafast charge separation process does exist in the actual solar cell devices, and the carrier generation in the device samples is similar to that of the film samples.
In the fourth part, two new nonionic crosslinked water / alcohol soluble polymers are used as separate negative electrode modified layer materials in the inverted organic electroluminescent devices. It is found that the efficiency of the inverted organic electroluminescent devices using the new negative electrode modified layer material is very high and can be compared with the best common structural devices. It is proved that the nonionic crosslinkable water / alcohol soluble polymer as a negative electrode modification layer has great value, and is worthy of being extended to the application of organic solar cells.
The fifth part of the work system studies the performance of five different ionic type water / alcohol soluble conjugated polymers as the negative electrode modification layer of the polymer solar cells. It is found that all materials can improve the properties of the common structure and the inverted structure polymer solar point devices in varying degrees, in which the amphoteric ion type materials and non ions are used. The performance of the type material is the best in the common structural device, and the free anion type material is the best in the reverse structure device, and the free cation type material reduces the performance of the device in the reverse structure device. We study the mechanism of the water / alcohol soluble conjugated polymer as the negative electrode modified layer from two theoretical models: ion weight. The new distribution theory and the interfacial electric dipole theory prove that the two aspects have contributed to the performance of the water / alcohol soluble conjugated polymer as the negative electrode modified layer, and the free anionic water / alcohol soluble conjugated polymer is the most suitable for the negative electrode modified layer material.

【学位授予单位】：华南理工大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TM914.4

【共引文献】