纳米ZnO薄膜掺杂改性及其在太阳能电池中的应用研究

发布时间：2018-03-01 22:14

本文关键词： 太阳能电池 ZnO材料掺杂改性第一性原理磁控溅射法前电极　出处：《江苏大学》2017年博士论文　论文类型：学位论文

【摘要】：光伏发电量在21世纪末估计将占到总发电量的一半以上,成为新一代清洁能源的发电主力,而薄膜太阳能电池在光伏电池中的占比正逐年上升。目前能源主要仍是由化石燃料提供,化石燃料在使用过程中会对环境造成较大污染,而且终会耗尽,因此太阳能作为取之不尽的能源并以“环境友好型”的特点从而将逐渐取代化石能源。然而现今太阳能电池一直存在着制备成本高、制备工艺复杂等问题;几种研究较为成熟的化合物太阳能电池,如砷化镓、碲化镉和铜铟镓硒等,由于砷和镉属于重金属对环境存在污染,铜铟镓硒材料来源有限等原因一直制约着太阳能电池向民用化的发展。ZnO作为一种新型半导体材料,在压电传感器、显示器、发光器件和太阳能电池方面都具有广阔的应用前景,而且ZnO属于环保无污染材料,而且自然界中储量丰富,在太阳能电池方面的应用具有巨大的潜力。本文以ZnO薄膜太阳能电池为研究目标,通过第一性原理理论对ZnO的n型和p型掺杂材料及相关浓度进行分析,找到较适合用作太阳能电池n型层、中间层和p型层的ZnO掺杂类型;然后通过磁控溅射的方式制备了 n型和p型掺杂ZnO薄膜,分析了其溅射功率、工作压强、衬底温度和以及气体氛围等重要工艺参数对薄膜结晶质量、表面形貌、导电特性和光学特性的影响;最后制备了 ZnO同质结和异质结太阳能电池,研究了中间层以及前电极对太阳能电池光伏性能的影响。本论文所做的主要工作和取得的研究成果如下:1.构建A1掺杂ZnO和In掺杂ZnO理论模型,发现两结构都属于服从费米分布的n型简并半导体,且A1掺ZnO的导电载流子浓度高达2.81×1021cm-3,可见光区理论透射率达90%,因此Al掺ZnO较适合应用于太阳能电池n结和透明导电电极。在对ZnO进行p性改性时发现采用Al-2N共掺结构的杂质能级较浅,Al-2N共掺ZnO结构中受主的自补偿作用得到降低,实现了 ZnO的p型转化;本文首次研究了稀土元素Eu的掺入对AZO在可见光区的吸收率影响,探索Eu掺AZO结构在太阳能电池中间层有无应用的可能性;2.采用磁控溅射的实验方法制备了 Al掺ZnO的n型薄膜、Al,N共掺的p型薄膜和Eu,A1共掺的ZnO作为太阳能电池中间层薄膜,与仿真的理论结果相结合,得到如下结果:(1)对薄膜制备关键工艺参数进行了研究,发现在溅射功率为120W、工作压强为2.0Pa及衬底温度为150℃时获得较好的结晶质量及光电特性;此外,制备薄膜的晶格常数、载流子浓度及透射率实验值变化趋势与仿真结果具有较好的一致性;(2)分析了 ZnO的p型转化机理,发现通过施主-受主共掺的方法可有效降低晶体的马德隆能量,制备一定浓度N20气氛下ZnOp型薄膜的透射率约为90%;发现达到最高性能的p型ZnO薄膜中Al、N比例约为1:2,与仿真结果具有较好的一致性;(3)制备了 Eu,A1共掺ZnO薄膜,发现ITO衬底上薄膜具有良好的导电性及透光性,并且在可见光区存在吸收峰,与理论计算中结果相一致;3.根据上述理论与实验相结合的结果,本文设计了不同中间层及前电极对ZnO太阳能结构光伏性能的影响:(1)研究了不同中间层对以Ti/Ag作为前电极的ZnO同质结(p型Al,N共掺ZnO/n型A1掺ZnO)及异质结(p型Si/n型A1掺ZnO)太阳能电池结构光伏性能的影响,结果发现:Eu,A1共掺ZnO作为太阳能电池中间层时具有最高的光电转换率,其中异质结太阳电池为1.467%,同质结太阳电池为0.426%,与理论预测相吻合;(2)研究了不同金属和AZO/金属/AZO结构前电极对p-Si/Eu,A1共掺ZnO/n-AZO异质结太阳能电池光电转换率的影响,发现Cr/Ni金属用作前电极时太阳电池光电转换率达6.68%,AZO/Cr/AZO用作前电极时太阳电池光电转换率高达7.11%;以上研究不仅对ZnO纳米薄膜的实验过程、制备机制、晶体结构、电学性质、光学特性等进行了较为系统的研究,也为ZnO薄膜型太阳能电池的实际应用提供了理论依据和实现可能。
[Abstract]:Photovoltaic power generation at the end of twenty-first Century is estimated to account for more than half of the total generating capacity, as a new generation of clean energy generation main, and thin film solar cells in photovoltaic cell in the proportion is rising year by year. The energy is mainly from fossil fuels, fossil fuels will cause great pollution to the environment in the process of using. It will be used up, so the solar energy as an inexhaustible source of energy and the characteristics of "environment friendly" which will gradually replace fossil energy. However, there has been a solar cell preparation cost is high, the problem of complex preparation process; compound solar cell, several mature study such as GaAs, cadmium telluride and copper indium gallium selenium, arsenic and cadmium are due to the existence of heavy metals pollution to the environment, forcigs materials limited sources and other reasons have been restricting the development of the solar cell to the civilian.ZnO As a new type of semiconductor material, the display in the piezoelectric sensor, and has wide application prospect of light-emitting devices and solar cells, and belongs to the ZnO environmental protection material, and nature reserves, has great potential in solar cell applications. In this paper, ZnO thin film solar cell as the research object, carries on the analysis the first principle theory of ZnO type N and P type doping concentration and related materials, to find suitable for N type solar cell layer, ZnO doping type intermediate layer and the p layer; then through magnetron sputtering method to prepare N and P doped ZnO films, analyzes its working pressure the sputtering power, and the important parameters of substrate temperature and gas atmosphere and the crystal quality of the film surface morphology, effect of conductive properties and optical properties; ZnO homojunction and heterojunction solar system was finally Study on the influence to the battery, the middle layer and the front electrode on the photovoltaic performance of the solar cell. The main work of this paper are as follows: 1. construction of A1 doped ZnO and In doped ZnO model, found that two structures belong to obey Fermi distribution N type degenerate semi conductor, and the concentration of conductive carriers A1 doped ZnO up to 2.81 x 1021cm-3, visible light transmittance theory up to 90%, so Al doped ZnO suitable for solar cell n junction and a transparent conductive electrode. In the ZnO P modified by Al-2N found that the impurity level Co doped structure shallow acceptor Al-2N Co doped ZnO in the structure of self the compensation effect is reduced, the P conversion of ZnO; this is the first study of the rare earth elements doping Eu on the effects of AZO on the absorption of visible light, explore the possibility of Eu doped AZO structure used in the middle layer of the solar cell by 2.; N film, Al doped ZnO were prepared by magnetron sputtering method experiment Al, N Co doped P thin films and Eu, A1 Co doped ZnO thin film solar cell as the middle layer, the combination of the theory and simulation results, the results are as follows: (1) the key process parameters on the preparation of thin film the research found that, when the sputtering power is 120W, the working pressure of crystallization quality and good photoelectric properties of 2.0Pa and substrate temperature is 150 degrees centigrade; in addition, the lattice constant of films, carrier concentration and transmission experimental value change trend and the simulation results are in good agreement; (2) analysis of the mechanism of P type the conversion of ZnO found by donor acceptor co doping can effectively reduce crystal Madelung energy, the preparation of ZnOp film transmittance of atmosphere under a certain concentration of N20 is about 90%; P type ZnO film reached the highest performance in Al, the N ratio is about 1:2, and the simulation results. There is good agreement; (3) to prepare Eu, A1 Co doped ZnO thin film on ITO substrate, that is conductive and good light transmittance, and absorption peaks in the visible region, consistent with the theoretical calculation results; 3. according to the combination of the theoretical and experimental results, this paper designs effect of different intermediate layer and the front electrode structure of ZnO solar photovoltaic performance: (1) were studied with Ti/Ag as the middle layer of the front electrode ZnO homojunctions (P Al, N Co doped ZnO/n type A1 doped ZnO) and heterojunction (P type Si/n type A1 doped ZnO), solar cell structure the results show that the photovoltaic performance of Eu, A1 Co doped ZnO as the middle layer of the solar cell has the highest photoelectric conversion rate, the heterojunction solar cell is 1.467%, homojunction solar cell is 0.426%, consistent with the theoretical prediction; (2) of different metal and AZO/ metal /AZO structure electrode on p-Si/Eu, A 1 Effects of Co doped ZnO/n-AZO heterojunction solar cell photoelectric conversion rate, Cr/Ni metal used as the electrode of solar cell photoelectric conversion rate of 6.68%, AZO/Cr/AZO is used as a front electrode when the solar photoelectric conversion rate as high as 7.11%; above research not only experimental process on the electrical properties of ZnO nano thin film, preparation mechanism, crystal structure. The optical properties were systematically studied, but also the practical application of ZnO type thin film solar cell provides theory foundation and realization.

【学位授予单位】：江苏大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TM914.4

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