有机太阳电池光学性能分析

发布时间：2018-11-29 14:09

【摘要】：随着人类社会对能源需求的逐渐增加,对气候问题的日益关注,太阳能作为一种清洁、可再生资源,受到越来越广泛的应用。有机太阳电池以其成本低、柔性好,可大面积制备等优点,成为一大研究热点,并在近些年的研究中取得了众多成果,在未来的发展中将具有巨大的应用潜力。有效层是有机太阳电池中实现光电转换的重要组成部分,其对光的吸收以及内部的辐射复合等情况都会影响电池的效率。对有效层光学性能所对应的光谱进行相应分析,可以在一定程度上为有机太阳电池的进一步优化提供方向,具有一定的研究意义。在本文中,基于目前主流的聚-3已基噻吩:苯基C60丁酸甲酯(P3HT:PCBM)材料做有效层的体异质结结构太阳电池,对有效层进行了紫外-可见吸收谱、光致发光谱及拉曼光谱行为的测试。通过分析,得到以下的结果:1.在P3HT:PCBM有效层中,主要的吸光物质是P3HT材料,其吸收主要源于其共轭结构中电子的π-π*跃迁,主要的吸收范围在300-650nm;其光致发光激发峰值位于640nm,710nm和780nm处。P3HT:PCBM较之P3HT材料,吸收曲线的吸收范围有所扩大,但可见光区域峰值位置呈现出短波长方向的偏移,同时吸收强度也有所减小;在光致发光谱方面,也出现了峰值蓝移现象及强度衰减现象。结合拉曼光谱分析可得,PCBM分子的加入使聚合物中的有序性遭到了破坏,吸收降低,峰值位置移动。但是从能级结构角度分析,能级的匹配与载流子迁移率的增强,使电荷的复合程度显示出一定的减弱,造成光致发光强度的衰减。通过改变P3HT:PCBM的比例,结合相应器件的电学测试结果,发现随着PCBM比例的增大,器件的开路电压逐渐增大,这种变化与有效层形貌变化引起的能级变动有关。当这一比例值为1:0.8时,电池的效率及短路电流密度达到最高值。对其光谱结果进行分析,其结果在于该比例下两者在有效层中所形成的交互网络最佳,从而使吸收与复合的综合效果最好。2.为了进一步提高有机太阳电池的效率,退火工艺被应用于器件的制备中。退火处理使P3HT:PCBM太阳电池的电学性能参数得到了显著的提高。通过光学性能分析可得,退火之后,P3HT:PCBM有效层的吸收曲线强度增强并且可见光区域的峰值位置向长波长方向移动,光致发光谱呈现衰减趋势,X射线衍射图呈现峰值强度的增强。这些结果显示,退火使有效层中P3HT聚合物的晶体化程度增大,两种材料产生相分离现象,同时迁移率也随之增大。当退火时长和温度增加时,相分离的距离会不断大,距离的增大会导致激子有效分离的效率降低,与此同时迁移率的增加会使电荷输运的效率增加。因此,在时长及温度的变化中,将会存在某一平衡点。经过光谱分析和器件测量可得,退火温度为150摄氏度、时长为15分钟应该为最优设置。
[Abstract]:With the increasing demand for energy and the increasing attention to climate, solar energy, as a clean and renewable resource, has been used more and more widely. Organic solar cells have become a research hotspot because of their advantages of low cost, good flexibility and large area preparation, and have made many achievements in recent years, and will have great application potential in the future development. The effective layer is an important part of photovoltaic conversion in organic solar cells. The absorption of light and the internal radiation recombination will affect the efficiency of the cell. The analysis of the spectrum corresponding to the optical properties of the effective layer can provide a direction for the further optimization of organic solar cells to a certain extent and has a certain significance of research. In this paper, the UV-Vis absorption spectra of the active layer of polyhexylthiophene: phenyl C60 butyrate (P3HT:PCBM) based bulk heterojunction solar cells are studied. Measurement of photoluminescence and Raman spectra. Through analysis, the following results are obtained: 1. In the effective layer of P3HT:PCBM, the main absorbent material is P3HT, whose absorption is mainly due to the 蟺-蟺 * transition of electrons in its conjugated structure, and the main absorption range is 300-650 nm. The peak value of photoluminescence excitation is at 710nm and 780nm. Compared with P3HT material, the absorption range of P3HT:PCBM is enlarged, but the peak position of visible region is shifted in the direction of short wavelength, and the absorption intensity is decreased. The peak blue shift and intensity attenuation are also observed in photoluminescence. In combination with Raman spectroscopy, the order of the polymer was destroyed, the absorption decreased and the peak position shifted with the addition of PCBM molecule. However, from the point of view of energy level structure, the matching of energy level and the increase of carrier mobility make the recombination degree of charge show a certain weakening, resulting in the attenuation of photoluminescence intensity. By changing the proportion of P3HT:PCBM and combining with the electrical test results of the corresponding devices, it is found that with the increase of the proportion of PCBM, the open circuit voltage of the device increases gradually, which is related to the energy level change caused by the change of the effective layer morphology. When the ratio is 1: 0.8, the cell efficiency and short-circuit current density reach the maximum value. The spectral results are analyzed. The result is that the interaction network formed in the effective layer is the best under this ratio, so that the comprehensive effect of absorption and composition is the best. 2. In order to improve the efficiency of organic solar cells, annealing process has been applied to the fabrication of organic solar cells. Annealing treatment improves the electrical properties of P3HT:PCBM solar cells. After annealing, the absorption curve of the effective layer of P3HT:PCBM increases and the peak position of the visible region moves to the long wavelength direction, and the photoluminescence spectrum tends to decay. The X-ray diffraction pattern shows the enhancement of peak intensity. These results show that annealing increases the degree of crystallization of P3HT polymers in the effective layer, resulting in phase separation between the two materials, and the mobility also increases. With the increase of annealing time and temperature, the distance of phase separation increases, and the efficiency of effective exciton separation decreases with the increase of distance. At the same time, the increase of mobility increases the efficiency of charge transport. Therefore, in the time and temperature changes, there will be a certain equilibrium point. The annealing temperature is 150 degrees Celsius and the duration of 15 minutes should be set optimally after spectroscopic analysis and device measurement.
【学位授予单位】：西安电子科技大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TM914.4

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