A strategy to repair two kinds of “holes” in perovskite “crystal building”

At the same time, a low-dimensional perovskite layer and a disulfide chelated passivation layer were constructed on the surface of perovskite, which effectively improved the stability of perovskite. Courtesy of Nanjing University of Technology

Professor Qin Tianshi’s team of the Institute of Advanced Materials research of Nanjing University of Technology used a kind of anion pair of materials to repair the two “holes” of the perovskite “crystal building”, passivating the defects of the perovskite material from many aspects and in all directions, changing the chemical properties, so as to achieve both efficiency and stability, and the relevant research results were “ammonium-quasi-halogen ion pair collaborative passivation perovskite surface preparation FAPbI3 perovskite solar cell” as the title, recently published in “Materials”.

Perovskite solar cells have high power conversion efficiency, comparable to the current commercial silicon solar cells, but because of their simple and more economical and environmentally friendly production process, they have become the “darling” of scientists around the world, and are expected to contribute to the realization of the double carbon target. What causes researchers a headache is that the current perovskite solar cells are still very sensitive to humidity, temperature, light and other environments, and when perovskite solar cells are exposed to these environments, they are prone to degradation, and there are outstanding problems such as poor stability.

At present, the research work on the market is mainly focused on solving unilateral problems to improve the efficiency and stability of solar cells, usually only optimizing for one of the components of perovskite materials, or optimizing a single chemical environment to achieve simultaneous improvement of efficiency and stability. Wang Aifei, co-first author of the paper and associate researcher, said that the team’s research results use the synergistic effect of adding anion pairs to passivate the defects of perovskite materials from many aspects and in all directions, and change the chemical properties to achieve both efficiency and stability.

Qin Tianshi explained that perovskite materials, like common table salts, are a crystal composed of anions and cations. In the microscopic world, this “crystal building” has many defects and holes, which will allow external water vapor to enter the interior of the building through the holes, and as the amount of water is increasing, the building will eventually collapse. From a macroscopic point of view, this perovskite crystal is broken down. Therefore, scientists have developed various materials to repair the defects of the building and protect it from external water vapor erosion. Just as anions together constitute crystals, the perovskite “crystal building” also has two kinds of “holes” of anion defects and cation defects, and the previous international peer work has only repaired one kind of hole. An anion and plasma are used to repair the material and repair two “holes” in the perovskite “crystal building” at the same time. The perovskite solar cells produced by this have greatly improved their efficiency and stability compared to the previously reported.

According to doctoral student Wang Jungan, the research results can achieve more than 23% of the photoelectric conversion efficiency under a standard sunlight, which is very close to or even exceeds the efficiency of current commercial silicon solar cells. At the same time, the synergistic effect of this anion to build two waterproof isolation layers can effectively improve the stability of perovskite solar cells, thereby extending the working time of the battery and achieving environmental stability of more than 1000 hours under continuous light.

“Through this research, a strategy to solve the pain points of multiple perovskite solar cells at the same time also increases confidence in trying to prepare larger area solar cells and prepares for the commercialization of perovskite solar cells.” Qin Tianshi commented.

It is reported that the first author of the paper is Wang Jungan, a doctoral student of Nanjing University of Technology, Ma Hongzhuang, a master’s student, and Wang Aifei, an associate professor, and the corresponding author is Qin Tianshi. (Source: China Science Daily Wen Caifei Jiang Pan)

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