Formulation Improvement And Device Fabrication Of High-Performance And Long-Life Perovskite Thin Film Solar Cell

Now,the non-renewable energy is over-exploited on the earth,resulting in environment pollution.In order to solve the serious energy and environmental problems that the society faced with,people brought forward the concept and purpose of clean,green,environmentally friendly and sustainable energy consumption.Solar energy,as a clean energy source,has always been one of the hotspots of research.The solar cell is one of the typical examples of solar energy conversion.To date,solar cell technologies and related products have constituted a large family.With the improvement and maturation of technology,there are more and more core materials that have been used for solar cells.Among them,perovskite materials have become a focus in this research field during the past few years.Because of its unique,excellent photoelectric properties and low cost,the perovskite solar cell has become a preferred device for power conversion.Japan’s Miyagi Power Group made the first organic-inorganic perovskite solar cells with 3.8%efficiency in 2009,and its efficiency is continuously refreshed in the following time.Last year,Korea’s KAIST’s Seok group succeeded in producing a small area perovskite solar cells with the efficiency of 22.7%.And just recently,Sweden EPFL has raised the record to 23.25%.However,organic-inorganic perovskite materials are extremely sensitive to humidity,oxygen,temperature,etc.The humidity in the air can easily damage the crystal structure of perovskite.The environment of fabricating the perovskite is also of strict demand.At present,the vast majority of high-efficiency perovskite solar cells are prepared with one-step method in the glove box.If they are transferred to ordinary air,the perovskite could be greatly influenced by humidity when the perovskite solution is spin-coated in air condition.The perovskite mineralization caused by the inconsistent crystallization rate leads to the collapse of the crystal system,but the detailed reaction mechanism needs further study.In addition,the lifetime of the perovskite solar cell is also a key issue.The efficiency of perovskite solar cells will decay since the organic-inorganic perovskite crystal will decompose under humidity.In this dissertation,we studied the change of perovskite via spin-coating in air environment and the method of prolonging the lifetime of organic-inorganic perovskite solar cells.At present,most of the high-efficiency perovskite solar cells are fabricated with one-step method.However,majority of the one-step methods will introduce other substances or artificial interference in the perovskite mineralization process.In order to avoid perturbation of perovskite,our experiments used vacuum crystallization in the mineralization process.The advantage of this method is that the perovskite crystals are pure and the process reproduction is better.We firstly investigate the vacuum crystallization conditions of perovskite of simple(e.g.,PbI2-MAI and PbI2-FAI)and other complicated multi-component precursor solutions(e.g.,PbI2-PbBr2-MAI-FAI),and test the power conversion efficiency.Then the next experiments combine the advantages of both of them.Finally,the formula of perovskite that we apply to solar cells developed to be a complex one with more than six components.At the same time,the stability and reproducibility of the perovskite solar cells prepared in air are greatly improved.Doping Cl element into perovskite precursor solution also improves the lifetime of perovskite solar cells.Apart from the quality of perovskite that determines the efficiency of the device,the thickness of each layer of the film can also play an important role.In the experiment of this dissertation,we enhanced the efficiency of perovskite solar cells by adjusting both the thickness of electron-extracting layer and the quality of perovskite layer.