高效CdSeTe量子点太阳能电池研究

发布时间：2018-02-08 13:31

本文关键词： 量子点敏化太阳能电池 CdSeTe量子点载流子传输与复合高效率　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】：量子点敏化太阳能电池(quantum dot sensitized solar cells,QDSCs)作为一种新型太阳能电池,因量子点敏化剂本身具有消光系数高、量子尺寸效应和多激子效应等优点使其光电转化效率有望突破传统的Shockley-Queisser极限,展现出巨大的发展潜力。近五年来,随着对QDSCs电池工作机制越来越深入的理解以及制备工艺的进步使其性能得到快速发展,目前其光电转换效率已经突破12%。但相比于当前被快速发展的钙钛矿太阳能电池和有机太阳能电池,QDSCs的效率仍然存在较大差距,如何进一步提升QDSCs性能仍面临很多挑战。对于QDSCs来说,无机半导体量子点作为吸光材料,其自身的光电性质、制备方法、表面缺陷、化学稳定性及其在TiO_2光阳极上的敏化方式等是影响电池性能的重要因素;而电池界面中严重的载流子复合更是成为制约电池性能的关键。本文以提高QDSCs效率为目标,基于CdSeTe合金量子点,从电池的光阳极结构、载流子的输运机制以及电解液改进等几个方面来开展工作。首先,采用有机溶剂热法成功制备出高质量CdSeTe胶体量子点,并通过配体交换将量子点吸附在TiO_2光阳极表面。详细研究了不同TiO_2光阳极结构对QDSCs电池性能的影响,通过优化光阳极结构使电池获得高达7.55%光电转换效率,这也是当时的最高效率之一;此外,还通过电化学阻抗谱,开路电压衰减等手段对电池界面载流子的转移过程进行了系统研究。在QDSCs中严重的载流子复合在很大程度上制约了电池性能,因此为了进一步提高QDSCs的效率,我们尝试将SiO_2纳米颗粒引入到电解液中以改善电池界面,从而减少界面载流子复合。结果表明,SiO_2纳米颗粒可以很好地分散在多硫电解液中形成稳定的胶体,并显著提高电池的开路电压和填充因子,将电池效率由8.7%显著提高到11.23%,这也是目前量子点电池的最高效率之一。此外,我们还对电池中电子传输和复合过程进行了系统研究,研究表明SiO_2纳米颗粒可以沉积在TiO_2/CdSeTe表面而形成能级势垒,有效减少了CdSeTe/TiO_2与多硫电解液之间的载流子复合,提高了电子收集效率和电子寿命。这一工作为改善QDSCs电池性能提供了一种简单方便又高效的方法。此外,我们初步探索了高质量CdSeTe合金量子点在固态量子点电池中的应用。首先,CdSeTe胶体量子点被分别吸附在具有不同晶相(锐钛矿相,金红石相或两者混合)的TiO_2介孔膜表面,并借助瞬态荧光激发谱和瞬态吸收谱研究了界面载流子转移情况。随后,尝试制备了结构为FTO/TiO_2/CdSeTe/空穴传输层/Au的固态量子点电池,其中CdSeTe量子点的沉积方法以及空穴传输材料(Hole transport materials,HTMs)的选择是整个电池的难点和关键。由于有限的TiO_2介孔层厚度导致CdSeTe沉积过少,目前电池只获得0.21 mA/cm2的短路电流和0.06%的电池效率。
[Abstract]:Quantum Dot sensitized Solar cells quantum dot sensitized solar cells QDSCs as a new type of solar cells, quantum dot sensitizers have a high extinction coefficient. The advantages of quantum size effect and exciton effect make it possible to break through the traditional Shockley-Queisser limit and show great potential in the past five years. With the deeper understanding of the working mechanism of QDSCs battery and the progress of preparation process, the performance of QDSCs battery has been developed rapidly. At present, its photoelectric conversion efficiency has exceeded 12. However, compared with the rapid development of perovskite solar cells and organic solar cells, there is still a big gap in the efficiency of QDSCs. How to further improve the performance of QDSCs still faces many challenges. For QDSCs, inorganic semiconductor quantum dots as absorbent material, its own photoelectric properties, preparation methods, surface defects, Chemical stability and its sensitization on the TiO_2 photocathode are important factors affecting the performance of the battery, and the serious carrier recombination in the battery interface is the key to restrict the performance of the battery. The aim of this paper is to improve the efficiency of QDSCs. Based on CdSeTe alloy quantum dots, high quality CdSeTe colloidal quantum dots were successfully prepared by organic solvothermal method in the aspects of photoanode structure, carrier transport mechanism and electrolyte improvement. Quantum dots were adsorbed on the surface of TiO_2 photoanode by ligand exchange. The effects of different TiO_2 photoanode structures on the performance of QDSCs cells were studied in detail. The photovoltaic conversion efficiency of the cells was as high as 7.55% by optimizing the photoanode structure. This was also one of the highest efficiencies of the time; in addition, through electrochemical impedance spectroscopy, Open circuit voltage attenuation and other methods are used to study the transfer process of carriers at the battery interface. The serious carrier recombination in QDSCs restricts the battery performance to a great extent, so in order to further improve the efficiency of QDSCs, We try to introduce SiO_2 nanoparticles into the electrolyte to improve the battery interface and reduce the carrier recombination at the interface. The results show that SiO2 nanoparticles can be dispersed in the polysulfide electrolyte to form a stable colloid. The open circuit voltage and filling factor of the battery are significantly increased, and the efficiency of the battery is increased from 8.7% to 11.23, which is also one of the highest efficiency of the quantum dot battery at present. In addition, we have carried out a systematic study of the electron transport and recombination process in the battery. The results show that SiO_2 nanoparticles can be deposited on the surface of TiO_2/CdSeTe and form energy level barrier, which effectively reduces the carrier recombination between CdSeTe/TiO_2 and polysulfide electrolyte. This work provides a simple, convenient and efficient way to improve the performance of QDSCs batteries. We have preliminarily explored the application of high quality CdSeTe alloy quantum dots in solid-state quantum dot batteries. Firstly, CdSeTe colloidal quantum dots are adsorbed on the surface of TiO_2 mesoporous films with different crystalline phases (anatase phase, rutile phase or both), respectively. The transient fluorescence excitation spectra and transient absorption spectra were used to study the carrier transfer at the interface. Subsequently, a solid-state quantum dot cell with the structure of FTO / TiO-2 / CdSeTe- / hole transport layer / au was prepared. Among them, the deposition method of CdSeTe quantum dots and the selection of hole transport material (Hole transport material) are the difficulties and keys of the whole battery. Due to the limited thickness of TiO_2 mesoporous layer, the CdSeTe deposition is too little. At present, only 0. 21 mA/cm2 short circuit current and 0.06% battery efficiency are obtained.
【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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