石墨烯量子点的可控制备及其在光电器件中的应用

发布时间：2018-01-15 00:34

本文关键词：石墨烯量子点的可控制备及其在光电器件中的应用　出处：《苏州大学》2015年硕士论文　论文类型：学位论文

【摘要】：石墨烯量子点(GQDs)是零维碳纳米材料,其量子限域效应和边缘效应显著,具有独特的光电传输特性。同时,它又具有石墨烯材料的优异性能,因而在光电子器件领域的应用前景非常广阔:如可调的光学带隙和光吸收使其在光电探测器和发光二极管器件上有极大的应用潜力,而高效的多重载流子产生和收集机制也使其在硅基太阳能电池上的应用有望突破Shockley-Queisser限制。然而目前大规模可控的GQDs的制备方法还不成熟,GQDs在光电子器件领域的应用也正处于起步阶段,因此,对GQDs在光电器件中的应用的进一步研究极其重要,这也是目前国际研究的热点问题之一。本论文主要针对GQDs的水热法制备及其在深紫外光电探测器和硅基太阳能电池中的应用展开了系统的研究。通过制备尺寸可控、溶液可加工的GQDs,来构筑基于GQDs的高性能深紫外光电探测器和平面硅异质结太阳能电池。主要研究内容和结论如下:一、利用水热法成功制备了尺寸可控且溶液可加工的GQDs。以石墨为原材料,首先运用改良的Hummer法制备氧化石墨烯碎片,然后将氧化石墨烯热还原成石墨烯片,接着在酸介质中氧化石墨烯片,得到浓度更高、尺寸更小的氧化石墨烯片,再用水热还原法制成小尺寸的石墨烯片,最后运用水热法将其切割成GQDs。此外,形貌和光学表征显示,合成的量子点尺寸均匀、可调且晶体结构很好,其带隙和发光特性都存在很强的尺寸依赖性。二、构筑了基于GQDs的深紫外光电探测器。利用GQDs可调的宽光学带隙特性,以溶液可加工的GQDs作为沟道材料制备的光电探测器能探测到254 nm的深紫外光。通过对器件能带结构以及载流子传输机制的研究,初步理解了器件的工作机理。同时,两边电极结构以及不同尺寸分布量子点对器件性能影响的研究表明,当量子点尺寸为2~6 nm且电极为非对称电极时,254 nm紫外光器件开关比可达到~6000,性能最好。量子点的高物理化学稳定性也使器件拥有优异的稳定性。简单、溶液可加工的器件制备过程和优异的器件性能使GQDs在未来高效、低成本深紫外光电探测器中具有巨大的应用前景。三、构筑了基于石墨烯量子点/平面硅异质结的高性能太阳能电池。由于GQDs独特的能带结构和载流子传输机制,光生载流子能够被有效分离,而量子点与硅形成的高电子势垒可以有效降低载流子的复合机率。通过对GQDs尺寸和薄膜厚度的优化,以及石墨烯透明电极的掺杂,我们制备了效率为12.35%的高稳定性石墨烯量子点/平面硅异质结光伏电池。这项工作显示了石墨烯量子点/硅异质结光伏电池在未来高效、低成本太阳能电池中的巨大应用潜力和研究价值。
[Abstract]:Graphene Quantum Dots (GQDs) are zero-dimensional carbon nanomaterials with remarkable quantum limiting and edge effects and unique photoelectric transport properties. At the same time, they have excellent properties of graphene materials. Therefore, the application prospect of optoelectronic devices is very broad. For example, the adjustable optical band gap and optical absorption make them have great application potential in photodetectors and light-emitting diode devices. And the efficient mechanism of generation and collection of multiplex carriers also makes its application in silicon based solar cells possible to break the Shockley-Queisser limit. However, at present, the large scale controllable GQDs. The preparation method is not mature. The application of GQDs in optoelectronic devices is in its infancy, so it is very important to further study the application of GQDs in optoelectronic devices. This is also one of the hot issues in international research. This thesis mainly focuses on the hydrothermal preparation of GQDs and its application in deep ultraviolet photodetectors and silicon based solar cells. Size controlled. Solution processable GQDs are used to construct high performance deep ultraviolet photodetectors and planar silicon heterojunction solar cells based on GQDs. The main research contents and conclusions are as follows: 1. GQDs with controllable size and processable solution were successfully prepared by hydrothermal method. Graphene oxide fragments were prepared by modified Hummer method using graphite as raw material. Then the graphene oxide is thermally reduced to graphene sheet, and then graphene oxide sheet with higher concentration and smaller size is obtained in acid medium, and then the graphene sheet of small size is prepared by hydrothermal reduction. Finally, the GQDs were cut into GQDsby hydrothermal method. In addition, the morphology and optical characterization showed that the synthesized QDs were of uniform size, adjustable and good crystal structure. The band gap and luminescence characteristics are highly dimensionally dependent. Secondly, a deep ultraviolet photodetector based on GQDs is constructed. The wide optical band gap characteristics of GQDs are used. The photodetector with GQDs as channel material can detect the deep ultraviolet light at 254nm. The band structure and carrier transport mechanism of the device are studied. At the same time, the effects of the structure of the two electrodes and the quantum dots with different size distribution on the performance of the device are studied. The results show that when the quantum dot size is 2 ~ 6 nm and the electrode is an asymmetric electrode. The switching ratio of 254nm ultraviolet light device can reach 6000nm, the performance is the best. The high physical and chemical stability of quantum dot also makes the device have excellent stability. Due to the fabrication process and excellent device performance, GQDs has a great application prospect in the future, which is high efficiency and low cost in deep ultraviolet photodetectors. High performance solar cells based on graphene quantum dots / planar silicon heterojunction were constructed. Due to the unique band structure and carrier transport mechanism of GQDs photogenerated carriers can be effectively separated. The high electron barrier formed by quantum dots and silicon can effectively reduce the probability of recombination of carriers by optimizing the GQDs size and film thickness and doping graphene transparent electrode. We have prepared highly stable graphene quantum dots / planar silicon heterojunction photovoltaic cells with an efficiency of 12.35%. This work shows that graphene quantum dots / silicon heterojunction photovoltaic cells will be highly efficient in the future. The application potential and research value of low-cost solar cells.
【学位授予单位】：苏州大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TB383.1;TN15

【相似文献】