What are the “consequences” of not listening to my senior sister? Become a professor at Wuhan University and publish world-leading achievements

Text | China Science Daily reporter Li Sihui correspondent Wu Jianglong

“You can choose anyone, but don’t choose Teacher Fang, he is very strict!” Every time I think of my senior sister’s words and my own “bias and disbelief in evil”, Ke Weijun, who is now a professor at Wuhan University, will secretly rejoice.

Fortunately, 10 years ago, he didn’t listen to his senior sister and applied for Fang Guoguo’s graduate school without hesitation, otherwise he would have missed a strict teacher and good teacher, and he would not have ushered in a “highlight moment” of his academic career so soon – on November 9, the journal Nature published online the latest research results on all-perovskite tandem solar cells by him and the team of Professor Fang Guoguo of Wuhan University. This achievement achieves one of the world’s highest efficiencies of all-perovskite tandem cells at both ends.


Fang Guoguo (third from left) and Ke Weijun (second from left) team in the laboratory. Li Sihui/photo
Senpai’s admonition

In the spring of 2011, Ke Weijun, a senior at Jiangxi Normal University, decided to apply for Wuhan University. There are many famous teachers in the School of Physical Science and Technology at the university, and he does not know which supervisor’s graduate students to apply for. After several rounds, he contacted a senior sister and humbly asked her for advice. The senior sister told him seriously and simply: “You can choose anyone, just don’t choose Teacher Fang, he is very strict!”

Later, he learned that the “Teacher Fang” in the mouth of the senior sister was called Fang Guoguo, who had been engaged in the research of thin-film solar cells for a long time. He has strict requirements for students’ learning and scientific research, and will regularly check the progress of scientific research, and does not allow students to waste their time.

“When I was admitted to Wuhan University from an ordinary university, I should be more diligent and hardworking than ordinary people, how can I be afraid that my tutor will be strict? The stricter the better!” As a result, Ke Weijun actively prepared for the exam and eventually became a student of Fang Guoguo. Ke Weijun sees this as an “important turning point” in his scientific career.

After entering Wuhan University, Ke Weijun made up for the shortcomings in his knowledge structure and devoted himself to study and scientific research. He found that his learning philosophy was highly consistent with Fang Guo’s training philosophy, and the teachers and students cooperated very tacitly.
Hot new material

Wuhan University is located on Luojia Mountain in Wuchang, and there are many historical buildings concentrated in the area halfway up the mountain. When the cherry blossoms are in full bloom, it is crowded with tourists. However, from studying for a doctorate to going abroad to engage in postdoctoral research, and then returning to Wuhan University to teach, Ke Weijun has not been to check in once in the past 10 years. It was only last autumn that he climbed Luojia Mountain for the first time.

“The main thing is that I am too busy, I spent most of my time reading literature and doing experiments when I was a student, and I was also in the laboratory on weekends and evenings, and I usually didn’t go out if I had nothing special. It is with this research energy that Ke Weijun has been recognized by his mentor.

In 2014, Fang sent Ke Weijun to the University of Toledo and the National Renewable Energy Laboratory for joint training. After graduating with a Ph.D., Ke Weijun successfully went to the research group of Mercouri G. Kanatzidis, a member of the American Academy of Arts and Sciences at Northwestern University, to conduct postdoctoral research until he returned to Wuhan at the end of 2020. During this period, he focused on a subdivision – the research of perovskite solar cells.

Ke Weijun told China Science Daily that solar energy is a very rich energy source, and solar cells are semiconductor devices that directly convert solar energy into electrical energy. At present, the mainstream semiconductor solar cells on the market are mainly silicon cells, but it still has some problems that need to be solved, such as the cost of power generation is not low enough. To reduce the cost of solar cell power generation, some new materials need to be developed, among which perovskite is a “big hit”. Compared with the silicon solar cells that are now commercialized, the cost of perovskite solar cells is expected to be significantly reduced, and they are one of the most promising next-generation solar cells.

In the past three years, Ke Weijun’s team has mainly focused on perovskite tandem solar cells. “‘Stacking’ means it’s going to be more efficient. Ke Weijun introduced.

Under normal circumstances, the photoelectric conversion rate of silicon is more than 26%, and after more than 10 years of development, the conversion efficiency of single-junction perovskites is comparable to that of the current single junction, but it is becoming more and more difficult to further improve the efficiency. If it is a tandem perovskite, the theoretical efficiency can reach more than 40%, which can further break through the efficiency limit of single-junction cells. How to maximize the efficiency of this transformation is the main direction of Ke Weijun’s team.

During the experiment, the research team discovered a special additive that can improve the efficiency and stability of solar cells at the same time when combined with perovskites, which solves the above two most critical problems and is expected to greatly reduce the LCOE of solar cells.

The inheritance of the strict teacher

Shun Zhou, the first author of the paper and a doctoral student in the team, said that in 2021, in an experiment, he stumbled upon an aspartate salt, which interacts with perovskites, which simultaneously improves the efficiency and stability of narrow-bandgap perovskite daughter cells in tandem cells. Zhou Shun happily reported the situation to his supervisor Ke Weijun and actively wrote his thesis.

What made him depressed for a while was that after the paper was written, Ke Weijun refused to submit the paper, and asked him again and again to do experiments and demonstrations again and again to ensure that every experimental data was impeccable.

Seeing that more than a year has passed, many classmates around him have published papers one after another, and he is still wandering between repeated failures in experiments and the strict requirements of his mentor, Zhou Shun began to be anxious. “Initially, I just wanted this article to be published in an international journal and have the opportunity to publish a better journal in the future. But Mr. Ke insists on excellence and repeated polishing, which is a bit of extreme perfectionism. Zhou Shun said.

When students are “emotional”, Ke Weijun will joke and ease the atmosphere, but the requirements will never be lowered. He said that Fang Guo’s “strictness” has benefited him for life, “Now that I am a teacher, I can’t mislead students, and I can be stricter when learning to do research, so that the efficiency and quality of scientific research can be higher in the future.” Once the requirements are relaxed, I feel that it is almost enough, and often the research stays in the second and third streams.”

In May this year, after several rounds of data correction, the team from Wuhan University simultaneously improved the efficiency and stability of the narrow bandgap perovskite daughter cell through the aspartate integrated doping strategy, and the tandem cell achieved a third-party certified efficiency of 27.34% (the scientific research team’s self-measured steady-state efficiency was 27.62%), which is one of the world’s highest efficiency of all-perovskite tandem cells at both ends.

At this point, Ke Wei agreed to submit the manuscript and submitted it directly to Nature. Nature reviewers praised the team’s research, but made dozens of revisions. Finally, after 5 months of revision and review, the paper was officially accepted. Zhou Shun finally breathed a sigh of relief, and sighed in the circle of friends, “Keep the clouds open and see the moon”.

There are strict and wide

In an interview with China Science News, Fang said that he and his team members began researching optoelectronic materials related to thin films in 2003. More than 10 years ago, when Ke Weijun was studying for a doctorate, he began to study the preparation of optoelectronic materials and devices. He believes that there is a lot of room for new batteries, including perovskite tandem solar cells, to be applied in the future, but there are still many scientific problems that need to be solved urgently. It is very meaningful to make world-leading research in this area.

To Fang Guoguo’s relief, his student Ke Weijun is now a teacher and has produced excellent results. What makes him even happier is that Ke Weijun not only continued his research, but also inherited the way he cultivated students.

Fang Guoguo said that he has always adhered to the principle of “strictness and leniency” in the training of students. In life, students should be “lenient” and more caring, but they must be strict in academic research. Students may not understand very well when they are studying, but once they go out into society, participate in work, or become teachers themselves, they can understand the meaning of strict requirements – making students more rigorous, learning more things, and getting more exercise, which will help a person achieve innovative results and breakthrough results.

Fang Guoguo believes that the publication of the results of Zhou Shun and others in Nature is a good example. Therefore, it is necessary to establish rules, clarify directions, set goals, and promote implementation in order to lay a solid foundation for students’ future scientific research careers.

“Where is that senior sister now? Do you regret not listening to her advice?” Facing the reporter’s question, Ke Weijun smiled heartily: “I have always thanked her for her kindness.” But I’ve always been glad I made that choice. In the process of going out to communicate, I will also meet some students who ask how to choose a tutor, and my advice is – maybe you can look for a teacher who is stricter. ”
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