South China University of Technology Publishes Major Perovskite Breakthrough in Nature

Research Background

Perovskite solar cells (PSCs) have become a research hotspot . Compared with traditional organic-inorganic hybrid perovskites, all-inorganic perovskites use inorganic cations (such as Cs+) to replace organic cations (such as methylammonium (MA+) and formamidine (FA+)), which have higher thermal and photostability. However, inorganic perovskites have problems such as uneven film crystallization, deep trap states and poor photothermal stability during the film formation process , which seriously restrict their application in efficient and stable solar cells. In particular, in all-inorganic perovskite stacked solar cells, the poor film morphology and deep trap states induced by tin ions lead to low efficiency of inorganic narrow-bandgap perovskite solar cells , which has become a major challenge in this field.

Research content

Professor Yan Keyou's team from South China University of Technology published a new paper titled "Durable all inorganic perovskite tandem photovoltaics" in the journal Nature, proposing a green ligand evolution (LE) strategy. By using p-toluenesulfonyl hydrazine (PTSH) as a ligand to regulate the nucleation and crystallization of perovskite films at low temperatures, Sn4+ was reduced to Sn2+ during high-temperature treatment, effectively reducing deep energy level trap states. At the same time, the product p-toluenesulfonic acid (PTSA) generated by the ligand further passivated the film defects . This strategy significantly improved the photoelectric performance of inorganic narrow-bandgap perovskites (CsPb0.4Sn0.6I3), and successfully prepared perovskite solar cells with a bandgap of 1.31 eV, achieving a record-breaking efficiency of 17.41%. Based on this, the team further combined the CsPbI2Br top cell with a bandgap of 1.92 eV to successfully construct a 2-terminal all-inorganic perovskite tandem solar cell, achieving an efficiency of 22.57% (certified as 21.92%).

Research highlights include:

• The experiment used a green ligand evolution strategy for the first time to regulate the nucleation and crystallization of all-inorganic narrow-bandgap perovskite films, successfully preparing the world's first two-terminal all-inorganic perovskite tandem cell and solving the problem of low efficiency of inorganic narrow-bandgap perovskite solar cells.

• The experiment prepared CsPb0.4Sn0.6I3 inorganic narrow bandgap perovskite solar cells with a band gap of 1.31 eV by optimizing the nucleation process of perovskite films and introducing ligands to passivate defect states, achieving a record-breaking efficiency of 17.41%.

• The experiment verified the excellent stability of the two-terminal all-inorganic perovskite tandem cell through photothermal stability tests, maintaining 80% of the initial efficiency in the 85°C photothermal aging test, showing photothermal stability that is better than that of organic-inorganic hybrid perovskite tandem cells.

【Summarize】

All-inorganic perovskite materials have significant advantages in improving photothermal stability and thermal stability, especially in the application of tandem solar cells, which demonstrates its potential to solve the problem of poor photothermal stability. This paper successfully overcomes the long-term stability problem in organic perovskite cells by replacing organic cations (such as methylammonium and methylammonium) with inorganic cations (such as Cs+). This strategy not only promotes the efficient application of all-inorganic perovskites, but also provides new ideas for the development of efficient and stable 2-terminal perovskite tandem cells . The introduction of the ligand evolution strategy provides a new technical path for the preparation of inorganic narrow-bandgap perovskite thin films. By regulating the ligand evolution, the researchers successfully adjusted the thin film crystallization process, reduced the deep energy level trap state, and improved the efficiency and stability of the perovskite cell. This method provides an important theoretical basis for solving the problems of inefficient thin films and deep trap states, and also lays a foundation for further improving the performance of inorganic narrow-bandgap perovskite solar cells.