Recently, the Chinese scientific research team successfully developed a pure phase two-dimensional perovskite film and its high-stability solar cell for the first time. The related research results were published in “Nature-Energy”.

Huang Wei, academician of the Chinese Academy of Sciences and chief scientist of the Flexible Electronics Frontier Science Center of Northwestern Polytechnical University, Chen Yonghua, a professor at the Institute of Advanced Materials, Nanjing University of Technology, and Xing Guichuan, a professor at the Institute of Applied Physics and Materials Engineering, University of Macau, reported for the first time through the coordination of precursor ions , The intermolecular interaction is adjusted to obtain a near monodisperse perovskite precursor micelle particle intermediate phase, and the pure phase two-dimensional perovskite film with different quantum well widths is obtained through solvent volatilization.

Huang Wei told the Chinese Journal of Science that this work was based on ionic liquids regulating the intermolecular interaction force, and for the first time realized an orderly oriented, two-dimensional pure-phase perovskite film with good crystallinity, revealing the pure-phase perovskite Film formation mechanism, optical characteristics, phase distribution and device performance.

In recent years, two-dimensional layered perovskite materials have become a research hotspot in perovskite solar cells due to their superior stability and photoelectric performance. At the same time, the two-dimensional layered perovskite film prepared based on the liquid phase method is composed of a multiphase mixed quantum well structure, that is, the target quantum well structure is very different from the actual multiphase mixed quantum well structure. Various other perovskite phase components have great limitations on the further application of perovskite devices.

Therefore, scientists have long been committed to preparing pure-phase two-dimensional perovskite films and studying their effects on the optoelectronic properties. In fact, although the perovskite precursor solution is configured in strict accordance with the stoichiometric ratio, it is still difficult to directly form a pure phase quantum well film of the target design during the deposition process.

The cooperative team innovatively used an ionic liquid organic amine salt to replace the traditional halogen organic salt to achieve effective control of the precursor solution ion coordination and intermolecular interaction, and obtain a micron-level two-dimensional layered perovskite film that is preferably grown , And can achieve effective inter-layer charge transfer, with excellent photovoltaic conversion efficiency of solar cells.

“The multiphase quantum well structure of perovskite has been successfully prepared by most scientific researchers. However, through the use of new ionic liquid organic amine salts and clever experimental design, a pure phase quantum well structure was obtained, and its optical characteristics and device performance were obtained. It’s the first time in the world to carry out in-depth analysis.” Chen Yonghua said, the analysis by grazing incidence small-angle X-ray diffraction technology showed that the pure-phase perovskite film prepared based on this technology has micron-level super-large grain size and good crystal Orientation and structural features are conducive to the improvement of device performance.

The single quantum well structure of the perovskite film is further confirmed by femtosecond laser spectroscopy. “The pure-phase two-dimensional perovskite exhibits a single bleaching peak and fluorescence spectrum is strong evidence of pure-phase quantum well.” Xing Guichuan explained, The pure-phase quantum well feature is discovered from the discrete and single optical feature, and the pure-phase film has a continuously adjustable phase distribution. This structure not only ensures the stability of the film, but also ensures the efficient transmission of carriers, which is a prerequisite for manufacturing high-performance devices.

At the same time, the planar solar cell device constructed by the researchers also shows that the pure phase quantum well structure significantly improves the stability of the two-dimensional layered perovskite solar cell. The pure-phase quantum wells demonstrated in this research will promote the development of solar cells and other perovskite-based optoelectronic devices (such as detectors, light-emitting diodes, lasers), and provide new ideas for further improvement of their performance.