Nature: large area high efficiency perovskite solar cell preparation

With the development of human society, the demand for energy is increasing day by day, while the traditional fossil energy such as coal and oil is gradually deficient due to continuous consumption, which leads to energy problems and also brings huge environmental problems Solar energy is inexhaustible Photovoltaic technology, which transforms solar energy into electric energy, has become one of the most potential technologies to solve the human energy crisis However, at present, the preparation cost of solar photovoltaic cells is high and the process is complex If there is no national policy support, it is difficult to achieve large-scale application Perovskite materials were first used in photovoltaic technology in 2009 In just a few years, the photoelectric conversion efficiency of perovskite solar cells in the laboratory has repeatedly made breakthroughs Its photoelectric energy conversion efficiency has rapidly increased to 22.1%, which exceeds the efficiency level of polysilicon solar cells, while the power generation cost is lower than that of silicon cells Therefore, perovskite solar cells are evaluated as the most competitive photovoltaic technology in the field of photovoltaic research, which is most promising to achieve low-cost power generation If the battery is to meet the practical needs, its key part - perovskite material film - should be large enough in area and good enough in film quality, so as to ensure that the photoelectric energy conversion efficiency of the battery is high enough The photoelectric energy conversion efficiency of polycrystalline silicon solar cells is about 21% At present, the area of perovskite solar cells with more than 20% certified efficiency can only reach 0.04cm 2-0.2cm2, which is at most as large as a grain of rice Moreover, the larger the area of perovskite films, the more prone to defects, and the lower the efficiency of the cells depend on the existing technology of preparing films Professor Han Liyuan, State Key Laboratory of metal matrix composite materials, School of materials science and engineering, Shanghai Jiaotong University, spent three years to solve this problem Based on the preparation of large area and high-quality perovskite films, an effective area of 36.1cm2 of perovskite battery module was developed The first certification efficiency of 12.1% was obtained in the international certification body, and the first large area of calcium titanium battery module was established World record for efficiency of mining modules The appearance of this achievement means that perovskite photovoltaic technology has the possibility of going out of the laboratory and realizing large-scale industrialization in the future Perovskite Thin film plays a key role in perovskite battery Its quality and performance directly determine the efficiency of the battery This requires the film to be very uniform, dense and crystallized However, in the battery device, perovskite film is very thin The ancients used to describe the thinness of things as "cicada wing" The thickness of perovskite film in the battery is dozens of times thinner than cicada wing Moreover, the structure of this material is relatively fragile The preparation process has a great impact on the quality of the film A little change of conditions will lead to many defects in the film and affect the electricity Photoelectric conversion efficiency of the cell The traditional preparation methods of perovskite films can be roughly divided into two categories: vacuum evaporation method and solution method The former is difficult to control the growth of the films, and the process is complex and the cost is high The latter is a commonly used method at present Organic solvents are used to dissolve perovskite powder into solution and make the solution into liquid film However, these organic solvents are generally irritant or even toxic, and large-scale use will bring environmental problems Moreover, organic solvent is a kind of foreign added component, which will have complex interaction with perovskite material, and it will be more difficult to remove in the later stage, which will also increase the cost and affect the quality of the film In order to make high-quality films, perovskite materials must be made into liquid for easy forming In the perovskite material composed of iodine, lead and ammonium formate, ammonium formate exists in the form of ions When ammonium formate meets ammonium formate molecules, chemical reactions will occur So the research team adopted a method to subdue the ammonium formate with ammonium formate: introduce the ammonium formate gas, let the ammonium formate molecule in the gas react with the ammonium formate ion in the perovskite material, and mix the product to get the liquid of the perovskite material This kind of liquid can quickly release the gas of methylammonium to become perovskite solid, and the released gas of methylammonium can be used again to react with the solid powder of methylammonium iodide and lead iodide to realize the recycling of materials The pressure processing method chart of Perovskite Thin film deposition (source: nature) in the preparation method of thin film, researchers also made innovations At present, high efficiency and small area (0.04cm2-0.2cm2) perovskite solar cells rely on the method of rotating coating solution to obtain high-quality perovskite films This method is a bit like "pancake spreading", and the preparation area is less than 25 The perovskite thin film of cm2 (5cmx5cm) has great technical advantages In the preparation of larger area of the thin film, because the rotation speed of different areas of the thin film is very different, it is easy to lead to pinholes, incomplete coverage, uneven thickness and composition of the thin film, which seriously affects the photoelectric conversion efficiency of the battery devices The one-time forming pressure assisted preparation method is adopted by halliway's team By controlling the pressure and coating the liquid material on the flat substrate, the uniformly distributed liquid film is obtained The new method of preparing large area uniform Perovskite Thin Film researched by halliwan team provides a new development direction for large-scale production of low-cost perovskite solar cell modules The team said that in the future, the research direction will apply the preparation technology of small area high-efficiency devices of the team to the modules, which is expected to achieve the module efficiency equivalent to the current silicon solar cells In addition, the stability of perovskite battery will be further explored to accelerate the commercialization process of the battery Combined with the above two points, the team hopes to make perovskite solar cells become the mainstream power generation mode in the market through their joint efforts and those of other researchers, so as to make contributions to reducing the cost of power generation, alleviating the energy crisis and improving the natural environment Paper link: http://www.nature.com/nature/journal/vaop/ncurrent/full/nature23877.htm