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Persistence is the key to success, the work of SJTU Prof. Xudong Yang’s team published again on Science!

SEPT 9,2022   

High-efficiency perovskite solar cells continue to set efficiency records, but their stability still faces significant challenges. On September 9, 2022, the academic journal Science published online the research results of Professor Xudong Yang's team in the School of Materials Science and Engineering of Shanghai Jiao Tong University, "Transporting holes stably under iodide invasion in efficient perovskite solar cells", which is an important progress in the research of stability issues in this field. Tao Wang, a PhD student in SMSE, is the first author of the paper, and Prof. Xudong Yang is the only corresponding author.

Science publishes online the research of Prof. Yang Xudong's team

Continuous breakthroughs in the stability of perovskite solar cells

Multiple publications in top journals

Prof. Xudong Yang has been working in the field of semiconductor physics and semiconductor materials for 20 years. After entering the research field of halide perovskite materials and devices, he has focused on the international problem of poor stability of the materials and devices, with emphasis on the deep mechanism and material properties, and on the painful problem of easy diffusion of iodine ions and destruction of battery performance, publishing first-unit corresponding author papers on key issues such as crystallization of perovskite thin films (Nature 2017, 550, 92) and structural stability of perovskite heterojunctions (Science 2019, 365, 687). The current published work is another challenge to the above scientific problems, focusing on the issue of iodine ion disruption of hole carrier transport, and has achieved a breakthrough in significantly improving the efficiency and stability of hole carrier transport.

Calcium Titanium Ore Photovoltaic is on the rise

Boosting the strategic layout of China's energy

With the development of society and population growth, the energy crisis and environmental issues are becoming more and more prominent, threatening the long-term survival and development of human beings. China has put forward the national strategy of "carbon peak" and "carbon neutral", and is striving to build a new energy lifeline led by clean energy. In this context, solar energy as a clean and renewable energy source has attracted much attention, and the photovoltaic industry has also ushered in a new opportunity for rapid development. Perovskite solar cells have gained widespread attention from the scientific and industrial communities for their superior photovoltaic performance, low manufacturing cost and simple preparation process. Its certified maximum efficiency quickly broke through to 25.7% in just 13 years, very close to the efficiency record of 26.7% for monocrystalline silicon solar cells, and moving toward a higher theoretical efficiency than crystalline silicon cells, showing great application prospects. Perovskite solar cells are composed of a perovskite light absorber layer, a hole transport layer and an electron transport layer, which generate photogenerated electrons and hole carriers with negative and positive charges respectively under light illumination to realize the conversion from light energy to electricity. However, the iodide component of the halide perovskite, which has a weak structure, tends to leave its original structural position, causing damage to the structure and performance of the perovskite, and further causing damage to the other functional layers of the cell. Among them, the diffusion migration of iodide into the hole transport layer will lead to the degradation of hole transport efficiency and interfacial energy level structure matching, thus causing significant degradation of cell efficiency, which is one of the currently unsolvable problems in the international frontier field.

A: Modulation of charge distribution of hole transport layer by ion exchange strategy; B: Hole conductivity enhancement; C: Energy level distribution modulation; D: Schematic diagram of energy level distribution; E: Conductivity under thermal aging at 120 degrees; F: Conductivity under iodine ion intrusion.

In the present work, Prof. Xudong Yang's team reports the stabilization strategy and intrinsic mechanism of hole transport in perovskite solar cells. By ion-exchange strategy, the team ion-couples the positively charged polymer with the introduced anion, which can effectively counteract the damage of the hole transport channel by the invading iodide, resulting in a significant enhancement of the conductivity and stability of the hole transport layer, which can also withstand high-temperature thermal stresses up to 120°C. The perovskite solar cells prepared based on this ion exchange strategy obtained a certified efficiency of 23.9%, the highest certified efficiency for non-lithium ion doped and PTAA-based perovskite solar cells. The cell still maintains 92% of the initial efficiency after 1000 hours of operation at maximum power point under standard sunlight and 85°C. This work provides an important scientific and technical basis for solving the stability problem of high-efficiency perovskite solar cells.

This research work was supported by Research Fellow Zhiliang Yuan of the Beijing Institute of Quantum Research, Professor Rongkun Zheng of the University of Sydney, Research Fellow Han Chen of Shanghai Jiao Tong University, and Associate Professor Qifeng Han. It was Supported by the National Key R&D Program of China (2018YFB1500104), the National Natural Science Foundation of China (11574199, 11911530142), the Special Zone Program of Shanghai Jiao Tong University, and the Shanghai Distinguished Professorship of Oriental Scholars.

Future Prospects

With the encouragement of the national policies of "carbon peaking" and "carbon neutral" and the background of global energy and environmental issues, the scientific research and industrial technology in the field of perovskite solar cells in China have been flourishing. The team believes that with the joint efforts of academic and industrial workers, the scientific and technological challenges of perovskite photovoltaic stability will be effectively solved to promote the realization of China's dual carbon goals and energy strategy.

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