The liquid crystal method enables large-scale production of uniform perovskite nanocrystals

The research team at Postech has developed a method for synthesizing the next-generation semiconductor material Perovskite nanocrystals (PNCs) in a more uniform and efficient way. This study overcomes the complexities of traditional synthesis methods and serves as a key breakthrough in accelerating the commercialization of various optoelectronic devices such as nanocrystal-based optical light-emitting diodes (LEDs) and solar cells. It is expected to be.

This study was conducted with doctoral degrees by Professors Young-Ki Kim and Professor Yong-Young Noh of the Faculty of Chemical Engineering at Postech. Candidates Jun-Hyung IM, Myeonggeun Han (Samsung Electronics), and Dr. Jisoo Hong (Princeton University). This study was recently published in ACS Nano.

PNC has great potential for next-generation solar cells and highly efficient displays. This is because the ability to absorb and emit light can be precisely controlled based on particle size and shape through quantum confinement effects.

However, traditional methods used to synthesize PNCs such as hot injection and ligand-assisted recompensation (LARP) produce particles of uniform size and shape due to high synthesis temperatures and complex experimental conditions. There are limitations to this. As a result, additional processing steps were required to obtain particles with the desired properties, which reduced productivity and limited industrial applications.

The Posttech Research team has developed a synthetic method that uses liquid crystal (LC) as the solvent for the LARP method to accurately control the size and shape of PNCs. LC is the mesophase of materials with both fluidity like liquids and long-range molecular order like crystals. In the LC phase, the molecules are aligned in a preferred direction (defined by the director) leading to elasticity. Therefore, when external forces are applied to the LC medium, the LC molecules are redirected, producing a considerable amount of elastic strain.

Inspired by this property, the team accurately controlled the growth of PNCs by simply replacing the solvents of traditional LARP methods with LC, while maintaining other synthetic conditions. The elastic strain of LCS limited the growth of PNCs upon reaching LCS extrapolation (ξ), allowing for the mass production of uniformly sized PNCs without the need for additional purification processes.

The researchers also found that interactions between PNCs and ligands that bind to the surface of LC molecules play an important role in reducing surface defects. Because LC molecules have long rod-like structures, ligands can be placed densely between them. As a result, the ligand binds to the surface more tightly during nanocrystal formation, thereby minimizing surface defects and increasing luminescent properties.

Professor Kim said, “The synthesis methods developed by our research team are highly compatible with existing synthesis techniques such as ligand exchange and microfluidic synthesis, and are made from LEDs, solar cells, lasers, photodetectors, and more. Improves the performance of a variety of optoelectronic devices.

“This technology will enable large-scale production of uniform, high-performance nanocrystals at room temperature, and is expected to help accelerate the commercialization of nanocrystal-based optoelectronic devices.”