On September 16, Forbes China released the 2021 annual 30 Under 30 list, and in the list of 30 people in science and medical health, a name called Wang Rui appeared: 28 years old, Westlake University, distinguished researcher /doctoral supervisor.
Yes, this is a young PI from the School of Engineering of Westlake University, born in 1993, who left UCLA in April this year to join Westlake, and is the youngest doctoral supervisor introduced by Westlake University to date.
On September 22, 2020, at the 75th session of the United Nations General Assembly, China proposed to achieve carbon peaking by 2030 and carbon neutrality by 2060. A key step towards this goal is to make the most of renewable energy, especially solar energy.
Wang Rui's research direction is closely related to this.
One of the small goals he set for himself was to create China's own record of "chasing light" at Westlake University.
01, decoding Wang Rui, starting from perovskite solar cells
The Earth is 150 million kilometers away from the Sun and receives only one billionth of the Sun's enormous energy output. But just converting 0.01% of the light energy radiated by the sun to the earth into electricity can allow people all over the world to live normally for a day.
To capture this huge amount of energy, scientists have developed silicon-based solar cells that can convert solar energy into electricity, and the conversion efficiency that can be achieved is currently between 22% and 23%, and the highest record in the laboratory can reach 26%.
However, there are relative deficiencies in silicon solar cells, such as pollution in the production process, the material is not easy to bend, and the footprint is large. And in recent years, its conversion efficiency has obviously encountered a bottleneck. Finding a new material for solar cells is imminent.
In 2009, Japanese scientist Tsutomu Miyasaka made the first perovskite solar cell, when the conversion efficiency was only 3.9%. But just a decade later, its conversion rate in the lab quickly reached 25 percent or more, comparable to the speed of four decades of silicon solar cells.
And the preparation cost of perovskite solar cells is very low, and it can also be made into flexible materials that fit irregular surfaces.
Regrettably, however, this new material has not been able to replace silicon cells for commercialization.
Unlike monocrystalline silicon, which requires very high purity, perovskite materials have a high tolerance for defects, even if there is a little impurity, they can also get high efficiency, but it is precisely the impurity of the material that causes its stability to deteriorate, such as being very sensitive to air and moisture, and even light will cause the collapse of its structure. Therefore, the service life of perovskite batteries is very short, only a few hours of use at first, and then extended to a few days.
Therefore, how to improve the stability of perovskite batteries has become the focus of research by scientists from all over the world.
In 2016, Rui Wang entered the University of California, Los Angeles, where he studied under Professor Yang Yang. The latter is a well-known expert in the field of international photovoltaics and has been committed to the research of perovskite solar cells.
Wang Rui said: "What we have to do is to find the defects in the perovskite material, and then prescribe the right medicine to improve the conversion rate of perovskite solar cells." ”
02. The world's three major beverages and Wang Rui's new scientific discoveries
The unique charm of scientific research often lies in the difficulty of exploring the unknown and the great joy of sudden peaks and turns.
Wang Rui did not expect that his favorite coffee would one day become a breakthrough point in his research.
It was 2018, and he was chatting with the rest of the team over coffee, which was their most relaxing moment.
He suddenly said: "Coffee can make people emotionally stable, so can it make the 'mood' of perovskites more stable?" ”
Looking at the caffeine structure, he found that there were two functional groups on this structure, just as the team had previously found to control perovskite crystallization and make the material grow better.
When all was said and done, they tried to add caffeine to perovskite solar cells and found that the output power of the battery was really greatly improved! The results were soon published in Joule.
Continuing research, Wang Rui found that the physical defects of perovskites have been studied and improved by many people, but the surface defects have not been paid much attention to, and he is keenly aware that this is likely to be a key factor affecting the stability of the battery.
"If the capacity of the perovskite battery is compared to a bucket, the physical defect is like the bottom of the bucket, and the surface defect is the barrel wall, which determines whether the bucket can hold water, but the barrel wall determines how much water the bucket can hold." Therefore, surface defects are very important for perovskite batteries, which determine the stability and efficiency of the battery. ”
So, after caffeine, the research team designed two similar alkaloids for perovskite solar cells: theophylline and theobromine, to repair surface defects. Experimental results show that theophylline works better, and the battery sets a new record of 500 hours of continuous operation.
In 2019, the results appeared in Science magazine. Surface defects have become the focus of research in the repair of perovskite battery defects.
In February, Rui Wang and his partners again published their latest research in Science: organic conjugate cations reconfigure the edges of energy bands to improve efficiency and stability. They discovered the "dual personality" of organic molecules in perovskite, providing new ideas for the design of new perovskite materials in the future.
03, the three "small goals" of life, all for the "chasing the light"
"There is light in the heart, forge ahead!" This is Wang Rui's message on the personal homepage of the official website of Westlake University.
This light illuminates his future and the future of our lives.
For example, using the flexible nature of perovskite solar cells, a layer of solar cells can be laid on smart cars to achieve infinite cycle charging; for example, although it is afraid of water and oxygen, there is no water and oxygen in space, which may become a place where it will show its fists in the future.
After joining Westlake University, Wang Rui's first small goal is to let perovskite solar cells go out of the laboratory and completely realize commercial applications.
Substrate preparation
"If the perovskite solar cell is combined with other traditional solar cells, the traditional solar cell is used as a bottom, and a perovskite battery is added to the top to make a laminated cell, the conversion efficiency of the battery connected in series is likely to exceed 30%, which is far more than the conversion efficiency of the solar cells currently on the market, and achieve the goal of 1+1>2."
At present, research teams all over the world are moving towards this goal, and there are more than 5,000 papers in the field of perovskite solar cells every year, which shows how fierce the competition is!
"It's good to have competition, which means that there is more wisdom and strength focused on contributing in this area, which can greatly accelerate the development process of perovskite solar cells." Everyone is climbing the mountain, they are about to climb to the top, and I hope that China is the first country to reach the top. ”
Wang Rui's second small goal is to create a record of "chasing light" that belongs to China.
Just like the Olympics, the solar cell field has its own record, about the length, about stability, about the size... China's research in the field of solar cells is very leading, but the start of superlay solar cells is relatively late, and there is currently no particularly outstanding world record on the Best Efficiency Chart.
"When I was in the U.S., I broke the organic solar record twice as a member of the main team, and of course it has been surpassed now, so I hope to be able to set a record for China on the stacked solar cell."
What is the last small goal? Strictly speaking, this may not be a small goal.
Wang Rui said: "Although Europe, China, and the United States have done a very good job in improving the function of perovskite solar cells, if one day this research wins the Nobel Prize, then I believe that the Japanese scientist who won this award is still the Japanese scientist, because he is the first person to do photovoltaic cell research with this material." ”
So far, Wang Rui believes that he has done all the work from 1 to 99, and he hopes that one day, he can make a 0 to 1 result, which is his true definition of "success".
Editor: Zhang Peng