The investigation was carried out by Professors Young-Ki Kim and Yong-Young Noh of the Chemical Engineering Department at POSTECH, in collaboration with Ph.D. candidate Jun-Hyung Im, Dr. Myeonggeun Han of Samsung Electronics, and Dr. Jisoo Hong from Princeton University. Their findings have been published in ACS Nano, an esteemed international journal in the field of nanotechnology.
PNCs offer significant potential for advanced solar cells and high-efficiency displays due to their tunable light absorption and emission, which can be precisely adjusted by particle size and shape through the quantum confinement effect. Traditional methods like hot-injection and ligand-assisted reprecipitation (LARP) frequently produce particles with inconsistent dimensions because of high synthesis temperatures and intricate experimental setups. This inconsistency often necessitates extra processing, thereby reducing overall productivity and limiting industrial applications.
To address these issues, the POSTECH team has adapted the LARP technique by substituting the conventional antisolvent with a liquid crystal (LC). Liquid crystals possess both fluid-like mobility and crystal-like molecular order, aligning along a preferred direction defined by a director to generate elastic forces. When external stress is applied, these forces reorient the molecules and produce significant elastic strains. By maintaining all other synthesis conditions while replacing the antisolvent with LC, the researchers controlled the growth of PNCs so that their expansion was halted upon reaching the extrapolation length (?) of the liquid crystals, enabling large-scale production without additional purification steps.
Further analysis revealed that the interaction between ligands attached to the PNC surfaces and the rod-like LC molecules enhances ligand packing. This denser arrangement minimizes surface defects and significantly improves the luminescence properties of the nanocrystals.
Professor Young-Ki Kim explained, "The synthesis method developed by our research team is highly compatible with existing synthesis techniques, such as ligand exchange and microfluidic synthesis, and will enhance the performance of various optoelectronic devices, including LEDs, solar cells, lasers, and photodetectors." He also stated, "This technology enables the large-scale production of uniform, high-performance nanocrystals at room temperature, and we anticipate it will help accelerate the commercialization of nanocrystal-based optoelectronic devices."
Funding for this research was provided by the Basic Research Program (Hanwoomul-Phagi Basic Research) and the Pioneer Program for Promising Future Convergence Technology of the National Research Foundation of Korea (NRF).
Research Report:Controlled Synthesis of Perovskite Nanocrystals at Room Temperature by Liquid Crystalline Templates
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