Just as in many fields, improving efficiency is an effective means to reduce costs, for solar cells, improving photoelectric conversion efficiency can effectively reduce the cost of photovoltaic power generation per unit area. However, even if the efficiency is improved, single-junction cells cannot break through the theoretical efficiency limit of 29% (silicon solar cells).
"Laminated batteries are like building blocks. You build one layer, and then build another layer. Since different semiconductors absorb light of different wavelengths, it can break through the theoretical efficiency limit of single junction cells, with a theoretical efficiency of more than 46%. "Li Hui, an associate researcher of the Superconducting and New Energy Materials Research Department of the Institute of Electrical Engineering, Chinese Academy of Sciences, said in an interview.
Recently, she collaborated with Wei Zhang of the University of Surrey in the United Kingdom to publish a cover article in the top international journal, "Chemical Reviews" with an impact factor of 52.758, comprehensively discussing the research progress of perovskite tandem solar cells.
"Work and life are the same as before. Scientific research is like building blocks. There are surprises and pressures." This 80-year-old scholar has won the Lu Jiaxi Young Talent Award of the Chinese Academy of Sciences, the first prize of Beijing Municipal Science and Technology Progress Award, and a senior Newtonian scholar of the Royal Society. Said later.
A "failed" experiment gave her unexpected gains
Li Hui said that perovskite tandem solar cells have the advantages of high conversion efficiency, low production cost, adjustable band gap, high structure and defect tolerance, etc., and can be combined with silicon cells or copper indium gallium selenium cells. Without increasing the cost, the actual photoelectric conversion efficiency of the battery can be further improved.
"When stacking stacked cells one by one, you must consider the following endurance, such as the highest temperature." Li Hui said, although there are currently some stacked cells on the market, such as gallium arsenide multi-junction solar Batteries, however, due to their strict manufacturing requirements and high cost, limit practical applications.
As early as 2017, Li Hui had the idea of ​​making laminated batteries. In 2019, when she was a visiting scholar at the University of Surrey in the UK, she mainly did research on laminated batteries. "The main thing is to optimize the performance of the sub-cell and the composite layer to obtain high efficiency, try to prepare a laminated solar cell without a composite layer, and reduce the cost of material preparation." She said.
easy to say, hard to do. "For example, copper-indium-gallium-selenium batteries are usually prepared by high-temperature co-evaporation methods, and the obtained polycrystalline films have large surface roughness, just like mountain tops and valleys. If the solution method is used to prepare perovskite batteries, the perovskite is easy to The valleys gather, and a continuous thin film cannot be formed, and a high-efficiency laminated battery cannot be obtained." Li Hui said.
To overcome these difficulties, she conducted a lot of experiments. "In order to reduce the roughness, to obtain a uniform and continuous coverage of the perovskite solar cell on the bottom cell, it is necessary to lower the preparation temperature. However, after the temperature is lowered, the conversion efficiency of the copper indium gallium selenide battery will correspondingly decrease, which requires While reducing the battery preparation temperature, it does not affect the conversion efficiency of the battery, which is a difficult point." She said.
A "failed" experiment gave her unexpected results. "During an experiment, because the actual temperature of the device did not reach the set value, the surface roughness of the prepared battery was significantly reduced. At the same time, due to the doping of other metal elements, the conversion efficiency of the battery did not decrease." She said, This experiment also allowed her to find the perfect combination of preparation temperature and transformation efficiency.
Through cooperation with the University of Oxford and the University of Surrey, and with the help of theoretical research, Li Hui and the others learned that the highest practical efficiency of the copper indium gallium selenide/perovskite tandem cell can reach 30.9%.
Let scientific research results out of the laboratory
Although Li Hui studied in different universities and research institutes for masters, doctors, and postdoctoral students, the research ideas she was taught were the same, that is, to find the research direction, make research results, and promote the transfer and transformation of experimental results, and truly serve The main battlefield of the national economy.
Li Hui introduced that there is still a long way to go from the laboratory to the application of perovskite tandem solar cells, such as solving the problems of stability and environmental protection. She will continue to cooperate with universities to further improve the conversion efficiency and stability of copper indium gallium selenide/perovskite tandem solar cells.
In addition to researching laminated cells, she will continue to carry out research on color photovoltaic films that can be applied to integrated building photovoltaic scenarios.
"By applying photovoltaics to buildings, we can adjust the color of the colored photovoltaic film to achieve a perfect combination with surrounding buildings. If the building is blue, we will make the film blue. In the early stage, we cooperated with the company to develop some low-cost colors. The membrane has been initially applied.†She said.
In addition, she will continue to cooperate with enterprises to explore the integration of production, learning, research, and application for the transfer and transformation of results, and participate in the establishment of photovoltaic industry standards.
Improve efficiency, cleverly balance scientific research and family
"I like doing research very much, and I can always find some new phenomena. This is very happy. But doing research, there must be a low period, that is, a short few days, find a way such as listening to music, running and venting. It's over." When asked how to balance scientific research and family, Li Hui smiled, "My child is now in elementary school and has to take care of the child, so I have to improve the efficiency of the experiment during the day, and after tutoring the child at night, I can Look at the literature and write something."
Although the family will involve some energy, Li Hui believes that women also have advantages in scientific research. "For those of us who are engaged in research, if an experiment is designed, it will generally have the expected results, but in the course of the experiment, you may encounter some unexpected situations. If you can capture these data, you may be able to get a comparison. Expect better results, just like Madame Curie discovered radium by accident. Women are often more careful and better able to capture and discover some details.†She said. (Reporter Jiang Jing)
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