“the river is more red than fire at sunrise the river is as green as blue in spring. “As we all know the sun as the energy source of life on the earth endows the earth with vitality the driving force for social development. In today’s electrical network era how to effectively obtain energy from the sun has become an important issue in the progress of human civilization so the development of solar cells has attracted more more attention. Compared with traditional silicon-based solar cells perovskite solar cells have the advantages of simple manufacturing process strong light absorption defect resistance. At present the photoelectric conversion efficiency of single perovskite solar cell has gradually approached the s-q limit so it has a great application prospect. However the instability of moisture in the air ultraviolet light restricts the development of perovskite solar cells. The instability is mainly due to the internal defects gathered in the interface grain boundary so how to effectively suppress the defects to improve the stability of perovskite has become the top priority in the field of perovskite solar cells.
to solve this problem Professor Yang’s research group of UCLA Professor Zhu Jia’s research group of Nanjing University used a new type of polymerization assisted grain growth in the growth of perovskite layer Pagg) method can effectively reduce the defect density of perovskite enhance the stability of perovskite solar cells. The
schemes add polymer monomers into PbI2 precursor solution. In the process of PbI2 film formation the monomers polymerize the polymer is distributed on the grain boundary. In the following perovskite film formation process because the polymer has higher binding energy with Pb it is difficult to be replaced by methyl iodide so the polymer will tend to be located at the grain boundary. The polymer at the grain boundary can combine with the incomplete coordination PB to eliminate the defect sites. At the same time due to the higher binding energy between polymer Pb the reaction barrier increases the nucleation point decreases during crystallization which significantly increases the size of perovskite grains further reduces the number of perovskite grain boundaries. The structure formed by polymer chains perovskite grains is similar to that of reinforced concrete. Under the action of reinforcement (polymer) concrete (perovskite) becomes stronger more durable. The improved perovskite solar cell achieves 23% efficiency maintains 85.7% initial efficiency after 504 hours of continuous illumination. At the same time after 2208 hours of storage at room temperature 91.8% of the initial working efficiency can be maintained. The remarkable improvement of cell stability indicates the feasibility of polymer assisted perovskite grain growth the variety of polymer types functions provide room for further improvement. This research combines the dynamic growth process of organic polymer inorganic polycrystalline materials provides a new idea for improving the stability of perovskite solar cells.
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