钙钛矿太阳能电池电子和离子电荷动力学研究

发布时间：2018-01-05 08:12

本文关键词：钙钛矿太阳能电池电子和离子电荷动力学研究　出处：《中国科学院大学(中国科学院物理研究所)》2017年博士论文　论文类型：学位论文

【摘要】：太阳能光伏技术是解决目前日益严重的能源与环境问题的重要手段之一,对于优化能源结构、改善环境和促进可持续发展意义重大。发展更低成本、更高效率的太阳能电池一直是光伏研究的热点。太阳能电池经历了第一代晶硅、砷化镓到第二代硫系异质结薄膜,直至目前第三代基于新材料和新工作机理的新型薄膜太阳能电池。钙钛矿电池正是近几年被开发并得到迅速发展的一种新型光伏器件。液相沉积的钙钛矿(比如甲胺铅碘(CH_3NH_3PbI_3)、甲脒铅碘(CH(NH_2)_2PbI_3)及其合金化合物)多晶薄膜具有高的光吸收系数(105 cm-1),低的缺陷态浓度(1016 cm-3)和较长的载流子扩散长度。基于这些优异的半导体性能、高质量薄膜沉积以及器件结构和界面调控的实现,小面积钙钛矿电池的光电转化效率在短短数年内被提高到22.1%,与商业化的多晶硅、铜铟镓硒和碲化镉电池相当。然而,钙钛矿电池依然面临稳定性及可工业化大面积生产等诸多挑战。同时,在钙钛矿电池的发展过程中,对于其材料和器件的本质属性(激子VS非激子、敏化VS异质结)和反常的光电迟滞行为及其物理机制方面均存在争议。基于此,我们从电池的电子和离子电荷动力学的角度对该器件的基本物理性质进行和研究,并通过电荷动力学调控等手段获得了高的器件性能,取得了如下研究成果:(1)通过二次重结晶的手段制备了致密平滑的PbI_2薄膜,并最终获得了高质量的钙钛矿薄膜。在此基础上,将无空穴传输材料的钙钛矿电池效率在国际上率先突破了10%。进一步优化钙钛矿薄膜的沉积,将该电池效率提高到11.4%,为当时国际上的最高效率。(2)通过异质结模型研究了无空穴传输材料钙钛矿电池的电荷转移特性,发现该电池的电流-电压特性完全满足半导体结型模型。进一步推得了该异质结的理想因子A~2,表明该电池的电荷转移特性主要由钙钛矿耗尽区的复合特性决定。又通过控制薄膜的沉积条件,实现了对钙钛矿薄膜空穴浓度的调控,进而实现了对钙钛矿耗尽电势和内建电场的调控。这种载流子浓度和内建电势的可调控性进一步证实该电池是典型的异质结太阳能电池。(3)基于对钙钛矿电子输运过程的研究和理解,发现限制无空穴传输材料钙钛矿电池性能的主要原因在其背表面场的缺失。这种缺失会导致部分光生电子会通过扩散的方式自发地转移到Au电极上,进而与价带的空穴进行复合,形成严重的背表面复合。为了抑制此复合,通过原子层沉积(ALD)方法在钙钛矿吸收层和Au电极间引入了超薄的AlOx层,最终实现了器件光电流和性能的显著提升。(4)发展了脉冲调控的瞬态光电测量方法,即电泵浦-瞬态光电探测。利用该方法研究了钙钛矿秒的时间尺度的光电迟滞及其背后的微观物理机制。结果表明,钙钛矿电池在弱电压调控下,即可在其吸收层内形成负的内部电场,并逐步演化形成正电场。电池在开路电压演化过程中,亦存在该过程。进一步通过器件模拟发现,只有同时考虑电场驱动下的离子输运导致的界面掺杂和缺陷态效应才能完美解释上述时间相关的微观动力学过程。(5)为了系统研究钙钛矿太阳能电池中的电荷输运和复合动力学过程,发展了可调控的瞬态光电测量系统,并在半导体输运模型的基础上建立了适用于结型电池瞬态测量的物理模型。利用该系统,可以直接测量太阳能电池在其实际工作状态下(不同偏压和不同光照)的电荷输运和复合特性。进一步利用物理模型,可以定量地获得电池不同界面的电荷抽取和收集效率,从而为定性和定量研究器件性能及其物理机制奠定了技术基础。
[Abstract]:Solar photovoltaic technology is one of the important means to solve the energy and environmental issues have become more serious at present, to optimize energy structure, improve environment and promote the sustainable development of great significance. The development of lower cost, more efficient solar cells has been a hot research. The photovoltaic solar cell has experienced the first generation to the second generation of crystal silicon, GaAs Heterojunction chalcogenide until the current junction thin film based on the third generation of novel thin film solar cells, new materials and new working mechanism. The perovskite cell is a new photovoltaic device was developed in recent years and has been developing rapidly. The liquid phase deposition of perovskite (such as methylamine lead iodine (CH_3NH_3PbI_3), Pb (CH formamidine iodine (NH_2) _2PbI_3) and alloy compounds) polycrystalline films have high optical absorption coefficients (105 cm-1), low defect concentration (1016 cm-3) and long carrier diffusion length. Based on these excellent The performance of high quality semiconductor, thin film deposition and the realization of the device structure and interface control, photoelectric conversion efficiency of small area perovskite battery was increased to 22.1% in just a few years, and the polysilicon business, copper indium gallium selenide and cadmium telluride cell. However, the battery is still facing perovskite stability and industrialization the area of production and many other challenges. At the same time, in the development process of the perovskite cell, the essential attribute of the materials and devices (non VS exciton exciton, sensitized VS heterojunction) and abnormal photoelectric hysteresis behavior and physical mechanisms are controversial. Based on this, we from the electronic and ionic charge battery of basic dynamics the physical properties of the device and research, and obtained the high performance of the device through the charge dynamic regulation and other means, the research results obtained as follows: (1) by means of two times recrystallization Smooth and dense PbI_2 films were prepared, and finally got the Perovskite Thin Films of high quality. On this basis, the perovskite cell efficiency will hole transport materials in the first international breakthrough to further optimize the deposition of 10%. Perovskite Thin Films, will improve the efficiency of the battery to 11.4%, then the international highest efficiency (2.) by heterojunction model of charge hole transport material perovskite cell transfer characteristic, found that the current voltage characteristics fully meet the semiconductor junction model. The ideal factor A~2 further deduced the heterojunction, showed that the composite decided mainly by the characteristics of the battery charge perovskite depletion region transfer characteristics. Through deposition condition control film, realizes the control of Perovskite Thin film hole concentration, and then realize the depletion potential and electric field in the construction control of the current Zi Nong perovskite. And the built in potential regulation to further confirm that the battery is typical of the heterojunction solar cells. (3) the research and understanding of the perovskite electronic transport process based on restrictions found the main reasons of perovskite battery performance of hole transporting materials on the back surface field is missing. This loss will lead to part of the photogenerated electrons through the diffusion spontaneously transfer to the Au electrode, and the hole in the valence band compound, to form a serious back surface recombination. In order to suppress this compound, by atomic layer deposition (ALD) method and Au electrode layer between the introduction of AlOx ultrathin layer absorption in perovskite, finally achieved significantly improve the optical device the current and performance. (4) developed transient photoelectric measuring method of pulse control, electric pump transient photoelectric detection of perovskite second time scale by the method and the back of the micro optical retardation The concept of physical mechanism. The results show that the perovskite cell in the weak voltage regulation, can be in the absorption layer to form the internal electric field of negative, and gradually formed a positive electric field. The battery open circuit voltage in the process of evolution, there is also the process. Further simulations are found only when considering the electric field driven ion transport lead interface defects and doping effect can perfectly explain the state time microscopic dynamics related. (5) in order to charge system of perovskite solar cells in the transport and recombination kinetics, the transient development of photoelectric measuring system can be controlled, and the physical model of the semiconductor transport models were formulated based on established node battery transient measurement. Using this system, it can directly measure the solar cell in the actual working conditions (different bias and different illumination) of the charge transport and recombination. Further, using physical models, we can quantitatively get the charge extraction and collection efficiency of different interfaces of batteries, thus laying a technical foundation for qualitative and quantitative research of device performance and physical mechanism.

【学位授予单位】：中国科学院大学(中国科学院物理研究所)
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TM914.4

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