Important progress has been made in the research of inverted perovskite solar cells

Perovskites have become a potential material for low-cost and high-performance solar cells due to their long carrier diffusion length, long carrier recombination lifetime, and wide absorption range. After more than ten years of development, the photoelectric conversion efficiency of single-junction perovskite solar cells has been increased to more than 25%, providing a new way for the upgrading and transformation of the solar cell industry. Inverted flat plate structure devices are highly valued because they can be prepared at low temperatures, negligible hysteresis effect, high stability, and can be fabricated into tandem cells. However, due to the polymorphism and ionic characteristics of perovskite materials, there are a large number of defects in perovskites that lead to ion migration and carrier non-radiative recombination, and the defects are the main channels for water/oxygen permeation, which will significantly reduce the stability of perovskite films and even devices.

In the early stage, under the leadership of researcher Ge Ziyi, the organic optoelectronic materials and device team of Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, through thin film morphology regulation, carrier transport layer modification and new two-dimensional perovskite material design (Angew. Chem.Int. Ed. 2023, 62, e2022175; Adv. Funct. Mater. 2023, 2301956; Adv. Energy Mater. 2021, 11, 2101416;Adv. Funct. Mater. 2022, 10, 2210600;Infomat 2022, e12379; Nano Energy 2022, 93, 106800;Energy Environ. Sci. 2022, 15, 3630) and other means have greatly improved the efficiency and stability of perovskite solar cells. However, defects in perovskites and light-induced phase separation will significantly reduce the performance and stability of perovskite solar cells. In order to solve this problem, based on additive engineering, the team used deformable additives to optimize the colloidal size distribution of precursor solution, increase the grain size of perovskite film, release grain boundary residual stress, passivate lead, iodine and organic cation defects, and inhibit light-induced phase separation. In addition, additives optimize perovskite energy levels, thereby facilitating carrier extraction/transport and reducing trap-assisted recombination. The performance of perovskite solar cells prepared by this method was greatly improved, and the devices based on brominated perovskites (FA0.88Cs0.12PbI2.64Br0.36) and bromine-depleted perovskites (FA0.96Cs0.04PbI2.8Br0.12) obtained the best efficiencies of 23.18% and 24.14%, respectively, and the flexible perovskite solar cells based on bromine-poor perovskites also obtained excellent efficiencies of 23.13%, respectively. It is one of the highest values of flexible perovskite solar cells reported to date. This work provides new insights into passivation defects, stress relief, and inhibition phase separation in additive engineering, and provides a reliable method for the development of state-of-the-art solar cells.

The results were published in the internationally renowned journal Advanced Materials under the title “A Deformable Additive on Defects Passivation and Phase Segregation Inhibition Enables the Efficiency of Inverted Perovskite Solar Cells over 24%”. Lisa Xie, a postdoctoral fellow at Ningbo Institute of Materials, and Jian Liu, a master’s student, are co-first authors, and Professor Ge Ziyi and Liu Chang of Ningbo Institute of Materials are the corresponding authors of the paper. The above work is supported by the National Outstanding Youth Foundation of China (21925506), the National Natural Science Foundation of China (U21A20331, 81903743, 22279151, 22209192, 62275251) and the Postdoctoral Program (2022M713242). (Source: Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences)

Figure (a) Schematic diagram of the interaction between additives and perovskites; (b) J-V characteristic curve of rigid perovskite solar cells; (c) Flexible perovskite solar cell device structure and J-V characteristic curve

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