金纳米晶合成及其在量子点敏化太阳能电池中的应用

发布时间：2018-04-29 08:59

本文选题：Au纳米晶 + TiO2纳米棒阵列　；参考：《河南大学》2014年硕士论文

【摘要】：近几年来，量子点敏化太阳能电池（QDSSCs）由于其光电转换效率的快速提升，日益受到人们的关注。目前，Mn掺杂的CdS/CdSe共敏量子点敏化太阳能电池，光电转换效率已经达到5.4%，显示出较好的应用前景。另外，由于量子点具有激子倍增效应（MEG），即吸收一个光子可以产生多个电子-空穴对，其理论光电转换效率高达44%，有望突破Schockley-Queisser极限（31%）。尽管在量子点敏化太阳能电池领域开展了大量的研究工作，迄今为止，其最高光电转换效率接近6%，依然远远落后于染料敏化太阳能电池报道的最高转换效率（~11.5%）。主要原因在于其器件结构尚需改善、光吸收尚需进一步增强、载流子复合问题尚需进一步解决。近年来，，人们尝试在量子点敏化太阳能电池中引入一维纳米结构材料，期望利用纳米结构材料独特的光电特性提高量子点敏化太阳能电池的光电转换效率。在量子点敏化太阳能电池中，通常采用介孔的纳米颗粒薄膜作为其光阳极，分离后的光生电子在这些颗粒薄膜中采用一种“跳跃”的形式在纳米颗粒之间传输，这种传输方式会造成在纳米颗粒界面之间产生严重的复合，使得其光电转换效率难以提升。而一维纳米结构材料可以为光生电子提供直接的传输通道，通过在量子点敏化太阳能电池中引入一维纳米结构材料有望大幅度提高其光电转换效率。然而，就目前的研究现状而言，基于一维（1D）纳米结构的量子点敏化太阳能电池的性能并没有预期的好，主要是由于其较低的比表面积使得量子点的担载量较低。因此，增强光吸收是提高一维纳米结构基量子敏化太阳能电池的有效途径。最近，贵金属纳米颗粒金、银、铜的表面等离子体共振效应引起了研究者的高度重视。很多研究者利用金属纳米颗粒的光散射与局域表面等离子体共振效应（LSPR）实现了薄膜太阳能电池的光吸收与光电流增强。在第一种方式中，光照射在贵金属纳米颗粒表面直接发生散射，这种散射效应可以有效地增加光子在太阳能电池器件中的传播路径，从而达到增强太阳能电池光吸收的目的；在第二种方式中，贵金属纳米颗粒中的电子在光子的激发作用下，产生集体的电磁振荡，即等离子体共振效应，在金属/半导体肖特基接触附近并且处于激发态的电子能够在冷却前越过肖特基势垒而注入到半导体导带中。这种等离子体共振“热电子”注入效应被广泛应用在光催化和聚合物薄膜太阳能电池中提高光催化能力和器件的光电转换效率。但就目前的研究现状而言，很少有研究者尝试把这种等离子体共振引起的“热电子”注入现象应用于一维纳米结构材料基量子点敏化太阳能电池中。为解决一维纳米结构材料基量子点敏化太阳能电池中由于量子点担载量较低造成的光吸收较弱的问题，在本论文中，我们制备了分散性较好的金纳米晶，并将其引入到一维TiO2纳米棒的量子点敏化太阳电池中，期望能够利用其等离子体共振效应在一定程度上增强光电转换效率。具体开展了如下三个方面的研究工作：（1）金纳米晶的制备：利用柠檬酸钠还原法，调节柠檬酸钠的量以及反应时间，制备了尺寸为20nm，分散性较好的球形金纳米晶；采用晶种生长法，制备了长约为55nm、宽约20nm的金纳米棒。（2）金纳米晶在量子点敏化太阳能电池中的应用：通过水热合成法，以FTO为基底，在180oC生长TiO2纳米棒阵列，成功制备了金红石相的TiO2纳米棒阵列；通过连续离子层吸附与化学水浴法制得TiO2/CdS/CdSe/ZnS光阳极，调节连续循环反应的次数，最后得到最优光阳极结构为TiO2/15CdS/20CdSe/5ZnS，光电转换效率为1.66%；金纳米颗粒注入到优化结构的太阳能电池中，光电转换效率可以从1.66%增加到1.73%，提高了大约4.2%。（3） Au/TiO2纳米棒阵列复合结构光电性能的研究：利用原位生长法，在TiO2纳米棒上复合金纳米颗粒；XPS研究证实Au纳米颗粒与TiO2复合后有电子转移；I-t测试结果发现Au/TiO2复合结构在可见光（≥420nm）的照射下，可以产生明显的光电流。该部分的研究结果表明：在可见光的激发下，Au纳米颗粒的表面等离子体共振效应产生的热电子越过Au纳米颗粒与TiO2导带中的肖特基势垒注入到TiO2导带中，可以产生光电流。
[Abstract]:In recent years, quantum dot sensitized solar cell (QDSSCs) has attracted more and more attention due to its rapid increase in photoelectric conversion efficiency. At present, Mn doped CdS/CdSe co sensitive quantum dot sensitized solar cells have reached 5.4%, showing a better future. In addition, because quantum dots have exciton multiplier effect (M EG), that is, the absorption of one photon can produce multiple electron hole pairs. The theoretical photoelectric conversion efficiency is as high as 44%, which is expected to exceed the Schockley-Queisser limit (31%).
Although a lot of research work has been carried out in the field of quantum dot sensitized solar cells, up to now, the maximum photoelectric conversion efficiency is close to 6%, still far behind the highest conversion efficiency (~11.5%) reported by dye sensitized solar cells. The main reason is that the structure of the device needs to be improved, the optical absorption needs to be further enhanced and the carrier recovery is still needed. In recent years, people have tried to introduce one-dimensional nanostructured materials in quantum dot sensitized solar cells. We expect to improve the photoelectric conversion efficiency of quantum dots sensitized solar cells by using the unique photoelectric properties of nanostructured materials. In quantum dot sensitized solar cells, mesoporous nanoparticles are usually used. As the photoanode of the film, the photogenerated electrons after separation are transported between the nanoparticles in the form of "jumping" in these granular films, which will cause serious recombination between the nanoparticles and make the photoelectric conversion efficiency difficult to improve. One dimensional nanostructure material can be a photoelectron. To provide direct transmission channels, the introduction of one-dimensional nanostructured materials in quantum dot sensitized solar cells is expected to greatly improve their photoelectric conversion efficiency. However, the performance of a quantum dot sensitized solar cell based on one dimension (1D) nanostructure is not expected to be expected, mainly due to its lower performance. The specific surface area makes the loading of quantum dots low. Therefore, enhanced optical absorption is an effective way to improve one-dimensional nanostructure based quantum sensitized solar cells.
Recently, the surface plasmon resonance effect of gold, silver and copper nanoparticles in noble metal nanoparticles has attracted the attention of researchers. Many researchers use the light scattering of metal nanoparticles and the local surface plasmon resonance effect (LSPR) to realize the optical absorption and photocurrent enhancement of the thin film solar cells. In the first way, light is illuminated. The scattering of noble metal nanoparticles can effectively increase the propagation path of photons in solar cell devices, thus enhancing the absorption of solar cells. In the second ways, the electrons in the noble metal nanoparticles produce a collective electromagnetic oscillation under the excitation of the light. The plasmon resonance effect is injected into a semiconductor guide band near the metal / semiconductor Schottky contact and the electrons in the excited state across the Schottky barrier before cooling. This plasma resonance "Thermo Electron" injection effect is widely used in photocatalytic and polymer film solar cells to improve photocatalytic activity. However, as far as the current research status is concerned, few researchers have tried to apply the "hot electron" injection caused by this kind of plasma resonance to the one-dimensional nanostructured material based quantum dot sensitized solar cells.
In order to solve the problem of weak light absorption due to low quantum dots loading in one dimensional nanostructured material based quantum dot sensitized solar cells, we have prepared a better dispersive gold nanocrystal in this paper, and introduced it into the quantum dot sensitized solar cell of one dimension TiO2 nanorods, expecting to use its plasma. To some extent, the resonance effect enhances the photoelectric conversion efficiency. The following three aspects are studied concretely:
(1) preparation of gold nanocrystals: using sodium citrate reduction method to regulate the amount and reaction time of sodium citrate, the spherical gold nanocrystals with a size of 20nm and good dispersibility were prepared. The gold nanorods with a length of about 55nm and about 20nm width were prepared by the seed growth method.
(2) the application of gold nanocrystalline in quantum dot sensitized solar cells: the TiO2 nanorod array of rutile phase was successfully prepared by the hydrothermal synthesis method, FTO as the substrate and the TiO2 nanorod array in 180oC. The TiO2/ CdS/CdSe/ZnS photo anode was obtained by continuous ion layer adsorption and chemical water bath method, and the number of times of the continuous cycle reaction was adjusted. Finally, the optimal photoanode structure is TiO2/15CdS/20CdSe/5ZnS, the photoelectric conversion efficiency is 1.66%, and the photoelectric conversion efficiency can be increased from 1.66% to 1.73% in the optimized structure of the solar cells, which increases about 4.2%..
(3) study on the photoelectric properties of Au/TiO2 nanorod array composite structure: using in situ growth method to compound gold nanoparticles on TiO2 nanorods, the XPS study confirmed that the Au nanoparticles and TiO2 have electron transfer. The results of I-t test found that the Au/TiO2 composite structure can produce obvious photocurrent under the irradiation of visible light (> 420nm). Some results show that under the excitation of visible light, the thermal electrons produced by the surface plasmon resonance effect of Au nanoparticles are injected into the TiO2 conduction band of the Au nanoparticles and the Schottky barrier in the guide band of TiO2.

【学位授予单位】：河南大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TM914.4;TB383.1

【参考文献】