Researchers from Seoul National University, Daegu Gyeongbuk Institute of Science and Technology (DGIST) and Korea Basic Science Institute (KBSI) have developed a new method to mass produce ultra-high color purity perovskite nanocrystals (PeNCs), without the need for high temperature, vacuum, or specialized gas facilities.
In this new study, Seoul National University's Professor Tae-Woo Lee's research team proposed a new synthesis method that overcomes the limitations of existing PeNC production techniques and identified a previously unknown synthesis mechanism. Conventionally, high quality PeNCs have been synthesized using the 'Hot-injection' method, which involves injecting materials into a hot solution above 150 °C. However, this approach presented several drawbacks, including safety risks such as fire or explosion due to high temperatures and rapid temperature drops, as well as the necessity for specialized facilities to block oxygen and moisture. As an alternative, room temperature (20-25 °C) synthesis methods such as 'ligand-assisted reprecipitation' have been suggested, but they faced limitations where the rapid precipitation rate led to inconsistent quality and a sharp decline in productivity during mass production.
To overcome these challenges, the team developed the 'cold-injection' method, which allows for high quality PeNC synthesis under ambient conditions. The 'cold-injection' process is characterized by lowering the temperature to near 0 °C, offering the advantage of eliminating heat related safety issues. It also significantly reduces production costs as it does not require specialized facilities and is highly suitable for mass synthesis.
Notably, the team discovered the previously unknown 'pseudo-emulsion' mechanism. The pseudo-emulsion state, combined with the cold temperature environment, effectively slows down the crystal formation rate, suppressing the formation of defects and enabling the creation of highly crystalline, uniform PeNCs. This approach enables consistent high productivity, even when scaling up to mass production.
The team expects the research findings to substantially accelerate the commercialization of perovskite emitters. The developed 'cold-injection' method offers advantages in terms of mass synthesis. Even when scaled up to a large 20-liter reactor, the research team achieved near-unity PLQY (~100%), identical to results obtained at the laboratory scale (~ml scale).
Furthermore, PeLED using the PeNCs recorded an EQE of 29.6%, demonstrating excellent performance. Additionally, in collaboration with SN Display Co., a faculty-founded startup of Professor Tae-Woo Lee, the team fabricated color conversion films based on these mass-produced PeNCs and integrated them into actual tablet displays, providing a compelling demonstration of their commercial potential.
These findings represent a substantial advancement in the synthesis of high-quality PeNCs, offering potential for broad applications in display and lighting industries.
