铜锌锡硫基薄膜材料微结构的改善及其光电应用研究

发布时间：2018-04-29 21:30

本文选题：铜锌锡硫 + 微观形貌　；参考：《吉林大学》2017年博士论文

【摘要】：太阳能被认为是最经济和环保的可再生能源,基于光伏效应的太阳能电池由于能够直接将光照转换成电能,因而受到了广泛的关注。薄膜太阳能电池具有制备工艺简单,所需原材料少,便于携带等优点而被广泛研究。铜铟镓硒(Cu In Ga Se2,CIGS)和碲化镉(Cd Te)薄膜太阳能电池已经实现了产业化生产,但是生产这两种电池需要消耗大量的稀有金属和有毒重金属元素。锌黄锡矿结构的铜锌锡硫(Cu_2Zn Sn S_4,CZTS)基材料具有合适的光学带隙和超过104 cm-1的高吸收系数,其组成元素都是地壳含量丰富且无毒的,理论预测CZTS太阳能电池转换效率超过30%,因此,被认为是替代CIGS制备薄膜太阳能电池的理想吸收层材料。CZTS基太阳能电池的效率在短短二十年内就从0.66%提升到12.6%,但与CIGS电池效率相比还有很大差距。除了材料单一相范围小、存在较多杂相和缺陷等问题外,薄膜的晶体质量以及p-n结能带匹配问题也是导致其效率较低的主要原因。针对这两个问题,我们在本文中提出了改善薄膜微结构、提高晶体质量的技术途径,并在此基础上对界面能带排列和相关CZTS基光电器件应用进行了研究,取得了如下结果:1、通过磁控溅射单一CZTS靶材、调节快速热处理气氛中S/Se元素比例,制备了大晶粒、高致密的CZTSSe薄膜。我们采取高压固态反应技术制备四元单一相CZTS靶材,然后通过磁控溅射技术和快速热处理技术制备CZTSSe吸收层薄膜。通过优化快速热处理的升温速率,得到了平整致密的吸收层薄膜;通过调节退火气氛中S粉和Se粉的比例,可以实现对薄膜中S/Se元素含量、结构以及光电性质的控制。研究结果表明贫S富Se的薄膜晶粒尺寸比较均匀,其纵向贯穿的晶粒尺寸能达到2μm,并且薄膜具有1.13 e V的光学带隙和较高的迁移率,适合作为高效率电池的吸收层。用这种薄膜制备了标准结构的电池器件,其光电转换效率为3.38%。进一步的分析表明,晶体质量的提高减少了光生载流子在CZTSSe吸收层内部的复合,但严重的界面复合导致了器件的理想因子和反向饱和电流较大,进而影响了器件的开路电压和填充因子。2、通过向CZTS前躯体溶液中添加适量的高分子聚合物,提高了薄膜晶体质量,改善了吸收层与缓冲层和背电极之间的界面性能。研究了聚乙烯吡咯烷酮(PVP)添加量对溶液法制备CZTSSe薄膜形貌及电池器件性能的影响。发现添加剂对薄膜的组分和晶体结构没有太大影响,但是能明显提高CZTSSe薄膜的致密性和晶粒尺寸。PVP添加量为5 wt%时晶粒尺寸能达到5μm以上,但是过量添加会使薄膜中出现小晶粒层,而添加比例为1 wt%时得到的薄膜表面和断面形貌都比较好。用这种薄膜制备的CZTSSe电池效率为4.34%。相比于未添加PVP的标准电池(效率为2.24%)提高了很多。电池器件界面的优化减少了光生载流子在界面处的复合。因此电池的开路电压,短路电流以及填充因子都有所提升。3、利用XPS实验测量结合第一性原理计算阐明了CZTS/Zn O异质结界面能带排列结构及其物理机制。利用磁控溅射制备了CZTS/Zn O异质结,通过X射线光电子能谱实验测量和第一性原理计算分别得到了CZTS/Zn O异质结的能带偏移。发现该异质结的能带排列为I型对齐,而且导带偏移值很小。这种能带对齐方式能够减少光生载流子的界面复合,并且不会阻碍载流子的输运。从能带排列角度说明Zn O是一种潜在的无毒缓冲层材料。4、通过调节施加偏压,实现了对p?CZTS/n?Ga N异质结光电二极管在紫外和可见区光响应的调控,并阐明了响应机制。由于宽禁带半导体Ga N和Zn O具有相似的结构和性质,我们采用射频磁控溅射方法在n-Ga N基底上沉积一层p-CZTS薄膜,制备出p-CZTS/n-Ga N异质结光电二极管,并研究了它的光响应特性。发现通过调节施加偏压可以调制其光谱响应,不加偏压和加上反向偏压时其响应波长分别位于紫外光区和可见光区,用异质结能带排列可以很好的解释观察到的实验现象。5、采用凝胶技术制备了新型的Cu_2Mg Sn S_4薄膜,阐明了硫化温度对薄膜结构及光电性质的影响规律。发现Cu+、Mg2+、Sn4+三种阳离子在晶格中的占位是随机的。由于晶体结构对称性的提高,X射线衍射结果中只出现了闪锌矿结构的特征衍射峰。CMTS薄膜具有良好的电学性质和合适的光学带隙,适合作为薄膜太阳能电池的吸收层材料。
[Abstract]:Solar energy is considered to be the most economical and environmentally friendly renewable energy. Solar cells based on photovoltaic effect are widely concerned because they can directly convert light into electrical energy. Thin film solar cells have been widely studied with the advantages of simple preparation technology, less raw materials and easy to carry. Cu In Ga Se2, CIGS) and cadmium telluride (Cd Te) thin film solar cells have achieved industrial production, but the production of these two kinds of batteries requires a large number of rare metals and toxic heavy metals. The copper zinc tin sulfur (Cu_2Zn Sn S_4, CZTS) base material of the zine tin structure has the appropriate optical band gap and the high absorption coefficient of over 104 cm-1, and its constituent element All the elements are rich and nontoxic in the earth's crust. It is predicted that the conversion efficiency of CZTS solar cells is more than 30%. Therefore, it is considered that the efficiency of.CZTS based solar cells, which is an ideal absorbing layer for preparing thin film solar cells by CIGS, has been raised from 0.66% to 12.6% in just twenty years, but there is a big gap compared with the efficiency of CIGS battery. In addition to the small phase range and a large number of impurities and defects, the crystal quality of the film and the matching of the p-n junction band are also the main reasons for the low efficiency. In this paper, we put forward a technical approach to improve the microstructure of the thin film and improve the quality of the crystalline body in this paper, and on this basis, the interface is on the interface. The results are as follows: 1, by sputtering a single CZTS target by magnetron sputtering and adjusting the proportion of S/Se elements in the fast heat treatment atmosphere, the large and dense CZTSSe thin films are prepared. The high pressure solid-state reaction technology is used to prepare a single phase CZTS target of four yuan and then through magnetic control. CZTSSe absorption layer films are prepared by sputtering and rapid heat treatment. By optimizing the heating rate of rapid heat treatment, a smooth and compact absorption layer film is obtained. By adjusting the proportion of S powder and Se powder in the annealing atmosphere, the content of S/Se elements in the thin film can be realized, the structure and the photoelectric properties are controlled. The results show that the poor S is rich in Se. The grain size of the film is more uniform, its longitudinal grain size can reach 2 m, and the film has the optical band gap and high mobility of 1.13 e V. It is suitable to be used as the absorption layer of the high efficiency battery. The increase of the quantity reduces the composition of the optical carrier in the CZTSSe absorption layer, but the serious interface recombination leads to the ideal factor and the reverse saturation current of the device, which affects the open circuit voltage and the filling factor.2. By adding a proper amount of polymer to the body solution before CZTS, the quality of the film is improved. The effect of the addition of polyvinylpyrrolidone (PVP) on the morphology of CZTSSe film and the performance of the battery devices was studied. It was found that the additives had no great influence on the composition and crystal structure of the thin film, but it could obviously improve the density and grain size of the CZTSSe film. The grain size can reach more than 5 m when the amount of inch.PVP is 5 wt%, but a small grain layer will appear in the film with excessive addition, and the surface and section morphology of the film are better when the addition ratio is 1 wt%. The efficiency of the CZTSSe battery prepared with this film is higher than that of the standard battery without PVP (efficiency 2.24%). The optimization of the interface of the battery device reduces the recombination at the interface between the optical carrier and the carrier. So the open circuit voltage, the short circuit current and the filling factor of the battery have been improved by.3. Using the XPS experimental measurement and the first principle, the arrangement structure and physical mechanism of the CZTS/Zn O heterojunction interface band are clarified. The CZTS/Zn O heterojunction is obtained by X ray photoelectron spectroscopy and the first principle calculation. The energy band migration of CZTS/Zn O heterojunction is obtained. It is found that the band alignment of the heterojunction is I aligned, and the guide band offset value is very small. This band alignment method can reduce the interface recombination of the optical carrier and will not hinder the load. Zn O is a potential nontoxic buffer layer material.4. By adjusting the bias voltage, the p? CZTS/n? Ga N heterojunction photodiode is regulated by the ultraviolet and visible light response, and the response mechanism is clarified. The structure and properties of the wide band gap semiconductor Ga N and Zn O are similar. We deposited a layer of p-CZTS thin film on the n-Ga N substrate by RF magnetron sputtering. The p-CZTS/n-Ga N heterojunction photodiode was prepared and its light response characteristics were studied. It was found that the spectral response could be modulated by adjusting the bias voltage. The response wavelengths were located in the UV light region and visible respectively without bias voltage and the reverse bias voltage. The optical region, using the heterojunction band arrangement, can explain the observed experimental phenomenon.5. The new Cu_2Mg Sn S_4 film is prepared by the gel technique. The influence of the vulcanization temperature on the structure and photoelectric properties of the film is clarified. It is found that the occupying position of three kinds of cations of Cu+, Mg2+ and Sn4+ in the lattice is random. In the results of X ray diffraction, only the characteristic diffraction peak of sphalerite structure is found in the.CMTS film, which has good electrical properties and suitable optical band gap, which is suitable for the absorption layer of thin film solar cells.

【学位授予单位】：吉林大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TB383.2;TM914.4

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