One of the most efficient in the world, Wuhan University has made another breakthrough in this research

In the early morning of November 9, Beijing time, Nature published the latest research results of the team of Fang Guoguo and Ke Weijun from the School of Physical Science and Technology of Wuhan University on all-perovskite tandem solar cells. The title of the paper is “Aspartate all-in-one doping strategy enables efficient all-perovskite tandems”.

Zhou Shun, Fu Shiqiang, and Wang Chen, doctoral students of the School of Physical Science and Technology, are the co-first authors of the paper, Professor Fang Guoguo and Professor Ke Weijun of Wuhan University are the corresponding authors of the paper, and researcher Wang Weiwei, Dr. Meng Weiwei, doctoral student Zhou Jin, master’s student Lin Qingxian, and undergraduate student Zou Yuanrong of Wuhan University are the co-authors of the paper, and Wuhan University is the only signatory.

From right to left: Fu Shiqiang, Zhou Shun, Fang Guoguo, Ke Weijun, Wang Chen

The new metal halide perovskite is a crystalline material with the general formula ABX3, which has the advantages of simple preparation process, high defect tolerance, high absorption coefficient and long carrier diffusion length, which has attracted much attention in the field of optoelectronic devices and is considered to be one of the most promising photovoltaic materials in the next generation. Among them, the photoelectric conversion efficiency of single-cell perovskite solar cells is comparable to that of traditional silicon-based cells, but it will be more and more difficult to further improve their efficiency.
All-perovskite tandem cells can break through the Shockley-Quaiser efficiency limit of single-junction solar cells, with a theoretical efficiency of up to 44%, and there is still a lot of room for improvement in performance. The all-perovskite tandem cell is composed of the wide bandgap perovskite subcell at the top and the narrow bandgap perovskite subcell at the bottom.
Based on this, Fang Guoguo and Ke Weijun’s team improved the efficiency and stability of narrow bandgap perovskite daughter cells at the same time through the aspartate integrated doping strategy, and achieved one of the world’s highest efficiency of two-terminal all-perovskite tandem cells with a steady-state efficiency of 27.62% (third-party authoritative certification efficiency of 27.34%).

In this study, the researchers cleverly introduced aspartate hydrochloride (AspCl) into the bottom hole transport layer, perovskite light-absorbing layer, and upper interface layer, and developed an integrated doping strategy using the same molecular treatment. It is found that AspCl-SnI2 and AspCl-PbI2 have very low formation energy, which is conducive to the formation of intermediates or complexes, which greatly improves the quality of perovskite films. In addition to coordination with perovskite precursors, AspCl molecules also have strong intermolecular hydrogen bonds, and AspCl enriched at the upper and lower interfaces of perovskites also acts as a molecular lock between the interface between the perovskite layer and the transport layer, further improving the performance and stability of perovskite materials.
In addition, how to inhibit the spontaneous oxidation of unstable divalent tin metal ions in narrow bandgap perovskites is one of the huge pain points in the industry. The results show that AspCl can effectively inhibit the oxidation of divalent tin and reduce harmful tetravalent tin impurities. Further studies also show that the introduction of AspCl can passivate the defects of perovskite materials, adjust the Fermi level, and inhibit harmful ion migration, thereby enhancing the performance and stability of the device. This simple integrated doping strategy achieves multiple energies in one fell swoop, providing a promising method for improving the performance of narrow bandgap perovskite and all-perovskite tandem solar cells, and is also expected to promote the development of other optoelectronic fields.
The research was supported by the National Natural Science Foundation of China, the General Project, the Natural Science Foundation of Hubei Province and the Scientific Research Public Service Conditions Platform of Wuhan University.

In the past 3 years, the research results have been published as corresponding authors in Nature (1 paper), Nature Photonics (1 paper), Nature Communications (1 paper), Advanced Materials (4 papers), Joule (2 papers), and Matter (1 paper). ), Energy & Environmental Science (3 papers), Advanced Functional/Energy Materials (6 papers), ACS nano (1 paper), Science Bulletin (1 paper) and other authoritative journals.
Paper Links:https://www.nature.com/articles/s41586-023-06707-z

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