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钙钛矿太阳能电池（PSCs）因其高的光电转化效率，制备成本低廉，受到了全世界科研工作者的广泛关注。在PSCs的各个组成部分中，电子传输层用以传输电子和阻挡空穴，对提升电池效率和缓解磁滞现象具有重要作用。目前研究最多，电池效率最好的一类电子传输层材料是TiO2。其中，锐钛矿相TiO2（A-TiO2）是目前高效率电池普遍采用的电子传输层材料，但它仍然存在一些缺点。例如较低的电子迁移率，导致电子传输层和钙钛矿界面处的电子堆积，降低电池效率的同时，也造成磁滞现象。因此，人们尝试了多种手段来改善A-TiO2电子传输层的性能。金红石相TiO2（R-TiO2）具有较高的电子迁移率，与钙钛矿更优的晶格匹配度。但R-TiO2却鲜有作为电子传输层用于钙钛矿太阳能电池。另一方面，具有光散射作用的空心球材料也极少用于多孔层研究。综上，针对两方面问题，本文一方面设计制备了金红石相TiO2电子传输层，系统研究了制备工艺条件对电子传输层质量和电池性能的影响，研究了锐钛矿和金红石相TiO2电子传输层性能的差异。另一方面，制备TiO2空心球的多孔层，系统研究了空心球结构对PSCs的光电性能影响。主要研究结果如下：1. 采用制备简便，成本低廉的制备方法，成功制备了金红石相TiO2。通过调控沉积时间和烧结温度，调控TiO2的结晶性和表面缺陷态等。经过制备工艺的优化，500 oC烧结温度为500 oC 时获得的R-TiO2电子传输层表现出最强的电子分离能力，实现将光生电子由钙钛矿层快速传输到FTO（F掺杂的氧化锡）层，获得了最高效率为20.8%的PSC。2. 相较于A-TiO2，R-TiO2具有与MAPbI3更佳的晶格匹配度，和与钙钛矿前驱体溶液更好的浸润性。R-TiO2的电子迁移率也更高，捕获态密度更低。在IMPS和IMVS测试中， R-TiO2电子传输层的电池的电子寿命更长，激子扩散速率更快。R-TiO2组装的电池获得了更优异的光电转换性能，同时缓解了磁滞效应。3. 利用葡萄糖的水热缩合反应，制备了300 nm、400 nm和800 nm的碳球。分别以它们作为模板，制备了50 nm、100 nm和200 nm的TiO2空心球（TiO2 HS）。通过TEM、SEM表征手段发现这些空心球只有薄薄的一层外壳层，其上均匀分布着微孔。XRD图谱显示，空心球均为纯锐钛矿相TiO2。随着空心球尺寸的减小，电池光电性能逐渐增加。50 nm TiO2 HS 获得了最优的性能，有效消除了磁滞现象。研究发现，50 nm TiO2 HS制备的电池具有更长的电子寿命，更快的传输速率，它的电子抽离能力也是最强的。此外，50 nm TiO2 HS的空腔结构有效减少了缺陷态密度，减少了缺陷，同时吸附更多的钙钛矿。综上，50 nm TiO2提高效率的同时，有效消除磁滞。;Perovskite solar cells (PSCs) have received widespread attention from researchers around the world, owing to its ease of preparation, low cost and high efficiency. Among the various components of PSCs, the electron transport layer, which acts for transporting electrons and blocking holes, is critical. And it plays a vital role in improving cell efficiency and relieving hysteresis. The most widely used electron transport layer material is TiO2. Although TiO2 is a commonly used material for high-efficiency batteries, its application still has some problems. For example, lower electron mobility results in electron accumulation at the interface between the electron transport layer and the perovskite, thereby reducing efficiency and causing large hysteresis effect. Therefore, various means have been tried to further improve the performance of the electron transport layer. However, rare studies on rutile phase TiO2 (R-TiO2) have been conducted. In addition, for the mesoporous layer, very little research has been conducted on hollow sphere materials, which have light scattering effects. Therefore, in order to solve these problems, the rutile phase TiO2 compact layer was prepared, and the influence of preparation conditions on the compact layer and the battery was studied systematically. The difference of anatase (A-TiO2) and rutile phase structure was studied in detail, and their impact on the performance of the battery. Additionally, the TiO2 hollow spheres were prepared for mesoporous layers, and the influence of hollow spheres on the photoelectric properties of PSCs was studied in detail. The main findings are as follows:1. A rutile phase TiO2 compact layer was successfully prepared by a new TiO2 preparation method. The system regulates deposition time and sintering temperature. As the sintering temperature increases, the crystallinity of TiO2 becomes better, the oxygen vacancies decrease, and the roughness first decreases and then increases. The R-TiO2 compact layer sintered at 500 °C has the strongest electron separation ability, and can transmit the photogenerated electrons in the perovskite to the FTO as soon as possible. Thus, it obtains higher VOC and FF, thereby achieving an efficiency of up to 20.8%. In addition, the method is simple in preparation and low in cost.2. When R-TiO2 is compared with A-TiO2, R-TiO2 has a higher lattice matching degree with MAPbI3, and better wettability with the perovskite precursor solution. The electron mobility of R-TiO2 is also higher, and the density of trapped states is lower. In the IMPS and IMVS tests, the results show that the battery prepared by the R-TiO2 compact layer has a longer electron lifetime and a faster diffusion rate. Therefore, the R-TiO2 assembled battery achieves superior photoelectric conversion performance while greatly alleviating the hysteresis effect.3. Using carbon hydrothermal condensation reaction of glucose, carbon spheres of 300 nm, 400 nm and 800 nm were synthesized. Using these carbon spheres as templates, 50 nm, 100 nm, and 200 nm TiO2 hollow spheres (TiO2 HS) were synthesized. These hollow spheres have only a thin outer shell layer with uniform micropores on the shell. XRD patterns show that the TiO2 hollow spheres are pure anatase phase. As the size of TiO2 hollow spheres decreases, its photoelectric properties gradually increase. 50 nm TiO2 HS achieved optimal performance and eliminated hysteresis. The performance of the battery prepared by P25 as a control group was between 100 nm TiO2 HS and 200 nm TiO2 HS. The battery prepared by 50 nm TiO2 HS has a longer electron lifetime and a faster transfer rate. Its electron extraction capability is also the strongest. In addition, 50 nm TiO2 HS effectively reduces the density of defect states, which may be attributed to its cavity fraction, reduced defects, and the ability to adsorb more perovskites. Therefore, it is possible to improve the efficiency while eliminating hysteresis.
|王永玲. 高效电子传输层的制备及其在钙钛矿太阳能电池中的应用[D]. 中国科学院大学,2019.|
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