Energy crisis and environmental pollution have become the primary problems that hinder economic development, and they are also the focus of attention of all countries in the world。Among the many new energy technologies, solar cells (also known as solar power generation technology or photovoltaic power generation technology) have become one of the most promising directions for application。With the rapid development of photovoltaic power generation technology, hybrid halide perovskite has become the most promising new generation of photovoltaic materials。

　　In less than eight years, perovskite solar cells have gained 22.The photoelectric conversion efficiency of 7%, its performance has exceeded that of polysilicon solar cells, was selected by Science magazine as one of the top ten scientific and technological breakthroughs in 2013, and is known as "new hope in the field of photovoltaic", and is favored by many researchers。Among them, there is a 22-year-old Li Zongqi, a 2015 undergraduate majoring in materials chemistry from the School of Materials, Beijing Institute of Technology, under the guidance of his mentor, with his own diligence and efforts, he has his own position in the field of perovskite solar cell research。

　　May 24, 2018，Li Zongqi is a junior student，Under the guidance of Professor Chen Qi of the School of Materials，As the first author, he published his research results entitled "Cost Analysis of Perovskite Tandem Photovoltaics" (Cost analysis of perovskite PV stacks) in Joule, a leading journal in the field of energy。

The "seeds" of interest took root in BeiIT

　　When he was in high school, Li Zongqi had a strong interest in clean energy and solar cell related fields. Through the online MOOCs platform, he learned the latest foreign research technologies and research progress in this field by himself. Since the development of MOOCs in China was not perfect at that time, Li Zongqi's self-study was mainly carried out through the MOOCs platform。"Teaching in English was a great challenge for me at that time, in order to achieve better learning results, I would preview the course content before each class, so that I could have a deeper understanding of the knowledge during the class process.。I think this is the power of interest。Li Zongqi said。Even during the preparation for the college entrance examination, Li Zongqi also squeezed out time to continue studying and accumulated a lot of knowledge in this field, which laid a good foundation for him to enter the university and enter the laboratory to carry out research。

　　In 2015, with this seed of interest in "solar cells", Li Zongqi became an undergraduate student majoring in materials chemistry at the School of Materials, Beijing Institute of Technology, and the school's talent training model provided fertile ground for the germination of this seed。In the practical semester of the school every autumn, each college will tailor the corresponding practical courses for students according to the characteristics of different professional disciplines。

　　Li Zongqi's major in materials chemistry requires students to enter the lab in advance, gain an in-depth understanding of various scientific research directions, and explore their own interests and potential scientific research capabilities。The setting of this practical course makes Li Zongqi feel a little "small excitement".。He actively consulted the research directions of various research groups in the laboratory，After learning that Professor Chen's research group is currently focusing on the industrialization of perovskite solar cells，He took the initiative to communicate with Professor Chen Qi，And in the second semester of the sophomore year officially entered the research group，Under the guidance of Professor Chen Qi，Officially entered into the study of the production cost of laminated perovskite solar cells。Since then, Li Zongqi officially opened the Liangxiang campus class, Zhongguancun campus to do the experiment of the two campuses "rush" mode。

It's on paper. It's on paper. It's on practice

　　"When I first entered the laboratory, I still focused on learning basic knowledge, thinking that only with enough basic knowledge can I have a sufficient understanding of the experiment itself。Li Zongqi followed the previous learning mode and continued to learn knowledge related to semiconductors and solar cells through online open courses such as Edx, Coursera, and MIT。However, as theoretical knowledge was too abstract, Li Zongqi gradually realized that some problems encountered in learning could not be completely solved from theoretical courses, resulting in slow progress in scientific research。To this end, Li Zongqi and the instructor conducted in-depth communication, "Teacher Chen designated a research group leader for me, and asked me to assist the senior to complete the experiment content, familiar with the operation process of the experiment, and find problems in the practice process and try to solve them.。Professor Chen Qi provided a new idea for Li Zongqi。

In the picture, the left is Li Zongqi and the right is Professor Chen Qi

　　"In the preparation of the organic reagent to be used in the experiment, it needs to be purified in advance, in theory, it should be purified more times, the more pure the reagent, but this is not the case in actual operation.。In actual operation, the more times of purification, the reagent is more susceptible to oxidation and corrosion of the external environment, and these small experiences summarized from practice can not be replaced by theoretical knowledge in books。"In the process of the experiment, in addition to exercising their operational skills, but also to better combine theoretical knowledge and practical experience, the content of the research subject has a more intuitive understanding and a deeper understanding.。Li Zongqi suddenly opened his mind。

　　On the way to success, we often need perseverance and perseverance to overcome difficulties。When Li Zongqi initially received comments from the reviewers of Joule Journal, he was greatly "hit", which involved the change of calculation model, the replacement of research objects, the confirmation and update of all data bases, the modification of supplementary information, the redrawing of experimental data charts, and the modification of article statements。In the eyes of most people, it is almost impossible to complete the revision within the stipulated time of one month。However, Li Zongqi and his team partners did not give up, but quickly made a work plan and devoted themselves to the revision of the article。"What impressed me most was the design of the new calculation model. From 11 PM, we worked all night until 2 PM the next day after discussion and confirmation with Teacher Chen, we returned to the dormitory to rest.。Although it was hard work, within two weeks, we re-determined the calculation model, research object, core data and assumptions, which laid a good foundation for the revision of the paper。"Li Zongqi recalled。

　　During the winter vacation, Li Zongqi still completed the cost calculation of each research object and the production of the result chart according to the scheduled work schedule every day, and this state continued until the Spring Festival。"On the evening of the New Year's Eve, Teacher Chen was still confirming the rationality of the experimental data with me by phone。For Chen Qi teacher's sincere guidance, Li Zongqi is grateful。

A small budget produces a big article

　　"A steed cannot leap ten steps;A worn-out horse drives ten times, but it does not give up。Under the guidance of the teacher and the joint efforts of the team，Lee is the first author of a study titled "Cost Analysis of Perovskite Tandem Photovoltaics" published in Joule, a leading journal in the field of energy。In the paper, he analyzed in detail the production costs of two types of laminated perovskite solar cells，By forecasting the Levelized cost of electricity，LCOE)，The significance of the technology route of laminated solar cells for the industrialization of perovskite photovoltaics is discussed in detail，The possible technical trend of the future development of perovskite solar cells is also predicted。

　　Because of its adjustable band gap, perovskite materials can be combined with different light-absorbing materials to become laminated battery materials with excellent photoelectric properties。The study shows that the theoretical photoelectric conversion efficiency of perovskite/crystalline silicon solar cells and perovskite/perovskite solar cells can reach 39% and 34% respectively by adjusting the band gap of the perovskite absorption layer。

Figure 1 (A) shows the composition of PERC polycrystalline silicon battery materials;(B) consists of a single junction perovskite battery material;(C) Composed of perovskite/crystalline silicon laminated cell materials;(D) Composed of perovskite/perovskite laminated battery materials。

　　In the field of solar cell materials, the levelized kilowatt-hour cost (LCOE) is usually used to measure the cost of the power generation entity consumed per unit of power generation during the system life cycle, which is the cost estimation standard to determine whether the power generation technology can be commercialized。For perovskite laminated solar cell materials, although there is the possibility of commercialization, but there is no relevant LCOE measurement method and research。In view of this gap, Li Zongqi and his collaborators adopted a "bottom-up cost model" to estimate the preparation cost of perovskite photovoltaic modules and further calculate the LCOE of photovoltaic systems。Under specific assumptions, by comparing four representative PV modules (Figure 1), the study found that the material cost of perovskite PV modules was lower than that of polysilicon PV modules。

Figure 2 (A) shows the LCOE (cents/KWH) of the four devices;(B-E) is a subdivision of the LCOE composition of the four devices。

　　In addition, Li and his team members also conducted research on module efficiency and lifetime, and for the first time proposed the concept of LCOE decrease rate to guide and plan the technological development path of perovskite PV and laminate perovskite solar cells (Figure 2).。Their published papers provide a reference for the development direction of the perovskite solar cell field from the perspective of commercialization。

　　Looking back on the birth of his first SCI paper, Li considers himself lucky。"Although I have experienced the failure of the experiment, I can find a way to solve the problem in time under the guidance of teacher Chen, and when I encounter difficulties, I can get the help of teachers and research group partners, and my heart is full of strength.。Li Zongqi said: "In the undergraduate stage can enter the laboratory in advance, not only can expand the idea of solving problems in scientific research, but also exercise their team cooperation ability, which will benefit a lot for future scientific research work.。”

　　"By entering the laboratory in advance, undergraduates can find an outlet for knowledge through practice, which is one of the most effective means of knowledge internalization.。At the same time, in practice, improve students' scientific research appreciation, expand their vision and pattern, which lays an important foundation for training first-class composite talents。When talking about the training mode of students entering the laboratory at the undergraduate stage, Professor Chen Qi said so。