高效发光碳纳米点制备及其作为下转换材料在太阳电池上的应用研究

发布时间：2018-01-05 22:25

本文关键词：高效发光碳纳米点制备及其作为下转换材料在太阳电池上的应用研究　出处：《上海交通大学》2015年硕士论文　论文类型：学位论文

【摘要】：碳点类材料包括了纳米金刚石、石墨烯量子点和碳点(碳量子点和碳纳米点),作为一种环境友好型的发光材料一直是人们关注的热点。由于其良好的生物相容性以及优异的光学特性,在生物成像、化学离子检测、光催化等领域已经得到了广泛的应用。石墨烯量子点由于其独特的能带结构及良好的电子传输特性,已被作为电子分离及传输层应用到太阳电池上。目前,在太阳电池上应用的发光材料还包括了半导体量子点、稀土离子以及分子荧光材料等,这些材料主要是作为下转换层中的光子转换材料应用到太阳电池的前表面上。而关于发光碳点类材料作为下转换材料在太阳电池上应用的报道还非常少。本文主要围绕高发光量子产率碳纳米点的制备、性能表征、机理解释以及其在硅纳米线阵列太阳电池上的应用方面来展开。首先,我们选择柠檬酸作为碳源,乙二胺作为氮源,利用水热法制备出了发光量子产率为76.7%的发光碳纳米点。制备出的碳纳米点同时含有sp2石墨型碳和sp3无定型碳两种碳结构,其平均尺寸为3.7 nm,分别在239和348 nm处有两个明显的吸收峰,发射峰位位于439 nm,并且表现出了激发波长独立的特性。较大的斯托克斯位移使其吸收带和发光带的重叠部分很小,有效的降低了自吸收损失,适合在太阳电池上作为下转换材料应用。其次,我们对碳纳米点的ph效应做了详细的研究。发现碳纳米点的吸收和发光均会受到ph环境的影响,这主要是由碳点表面官能团在不同ph环境下的质子化和去质子化作用导致的,说明了碳纳米点的发光与其表面态有很大的关联。另外,碳纳米点激发独立的光学性质说明了碳纳米点表面态比较单一,有利于较高的发光量子产率。第三,我们首次通过在反应前驱物中加入氨水,使碳纳米点的发光量子产率达到了84.8%,相对于无氨水的情况提升了10.56%。我们通过借助x射线光电子能谱(xps)、傅里叶变换红外光谱(ftir)以及荧光寿命等手段,对不同氨水浓度条件下合成的碳纳米点的结构和发光量子产率之间的关系做了详细的探讨。研究发现,碳纳米点的发光量子产率与氧态成反比,与氮态和氧态的比值正相关。这主要是因为适量的氨水可以增强碳纳米点的表面酰胺键并能够有效的去除氧缺陷态,减少非辐射复合或低效辐射复合的途径,最终得到了高效发光的碳纳米点。最后,我们成功的将制备的碳纳米点作为下转换材料应用在了硅纳米线阵列太阳电池上。需要注意的是,固态的碳纳米点会由于其自身的聚合作用对表面态进行破坏,最终出现荧光淬灭的现象。为了解决这个问题,我们选择了能够与碳纳米点相融合的高透明度的聚乙烯醇作为碳纳米点的载体,并通过旋涂法在硅纳米线阵列太阳电池上制备出了在365nm紫外灯照射下发射蓝光的下转换层,使器件的短路电流密度提升了0.30ma/cm2。通过借助太阳电池外量子效率光谱,我们发现器件的提升来自于下转换贡献、光场重新分布和反射率上升三方面的综合结果。为了提取出下转换对器件性能提升的贡献,我们基于量子效率光谱建立了理论模型,定量提取出了下转换的贡献(43.3%)。
[Abstract]:Carbon materials include nano diamond, graphene quantum dots (QDs and carbon carbon and carbon nano dot), as a kind of environmentally friendly luminescent materials has been the focus of attention. Because of the compatibility and excellent optical properties of its good biological imaging in biology, chemical ion detection photocatalysis has been widely used. The graphene quantum dots due to their unique electronic band structure and good transmission characteristic, has been used as electron transport layer and separation applied to solar cells. At present, luminescent materials used in solar cells include semiconductor quantum dots, rare earth ions and molecules fluorescent materials, these materials are mainly as a down conversion layer in the conversion material applied to the front surface of the solar cell. And on the application of luminescent materials as carbon conversion materials in solar cells There are few reports. This article focuses on the characterization of the preparation, properties of high quantum yields of carbon nano point, explain the mechanism and its application in silicon nano wire array solar cells to unfold. Firstly, we choose citric acid as carbon source and ethylenediamine as nitrogen source, water heat produced by light the quantum yield of luminescence nano carbon 76.7%. Carbon nanodots prepared with SP2 type graphite carbon and SP3 non carbon two carbon structure shape, the average size is 3.7 nm, respectively in 239 and 348 nm has two obvious absorption peaks, the emission peak position at 439 and nm. Show the excitation characteristics of wavelength independent. The large Stokes shift and light absorption band overlap zone is very small, can effectively reduce the loss of self absorption, suitable for solar cell application as conversion material. Secondly, we point to the carbon nanometer pH. We should do a detailed study. The discovery of carbon nano point absorption and emission are influenced by the pH environment, which is mainly composed of functional groups on the surface of carbon protonation in different pH conditions and deprotonation result, illustrates the point and the surface of the carbon nano luminescent state has a great Association. In addition, carbon nano optical properties that stimulate independent carbon nano surface state is relatively simple, there is conducive to higher quantum yields. Third, we for the first time by adding ammonia in the precursor reaction, the luminescence quantum yield of carbon nano point reached 84.8%, compared to non ammonia water by raising the 10.56%. us through X ray X-ray photoelectron spectroscopy (XPS), Fu Liye transform infrared spectroscopy (FTIR) and fluorescence lifetime and other means, the relationship between the structure of carbon nano dots synthesized under different ammonia concentration and luminescence quantum yield in detail The study. The study found that the luminescence quantum yield of nano carbon and oxygen state is inversely proportional to the ratio of nitrogen and oxygen was related to the state and state. This is mainly because the amount of ammonia can increase the surface point of the amide bond of carbon nano and can effectively remove the oxygen defects, reduce non radiative recombination or inefficient radiation recombination way, finally get the point of carbon nano efficient luminescence. Finally, we successfully prepared carbon nano materials as used in the conversion of silicon nanowire array solar cells. Note that the carbon nano solid will point due to its cooperation with poly to destroy the surface state, eventually appearance of fluorescence quenching phenomenon. In order to solve this problem, we choose to merge with the carbon nano transparent polyvinyl alcohol as the carrier of carbon nanodots, and through spin coating on silicon nanowire array solar cell system Prepared in the 365nm emits blue light under UV irradiation under the conversion layer, so that the short-circuit current density increased by 0.30ma/cm2. solar cell by means of external quantum efficiency spectra, we found that the device upgrade comes from the conversion of contribution, light field redistribution and the reflectance increased from three aspects of the comprehensive results. In order to extract the conversion to improve the performance of our device contribution, the quantum efficiency spectra was established based on the theoretical model, quantitative extracted conversion contribution (43.3%).

【学位授予单位】：上海交通大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TM914.4;O613.71

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