Scientists from Korea’s Ulsan National Institute of Science and Technology (UNIST) have developed a simple technique to advance full-color perovskite LEDs.
Perovskite nanoparticles are regarded as the future of low-cost optical materials that can achieve vivid colors even on very large screens.
The institute recently introduced a simple technique to extract the three primary colors (red, blue, green) from this material. The breakthrough was led by Professor Jin Young Kim.
In the study, the research team introduced a simple technique that freely controls light emitting spectrums by adjusting the anion halides in perovskite materials.
The key lay in adjusting the anion halides by simply dissolving them in solvents to achieve red, blue, and green lights.
Perovskite nanoparticles are microscopic perovskite materials at nanometer (nm, 1 nm/1 billionths of a meter) level, which emit different colors depending on the internal halogen element.
It is a formula that emits red when it is rich in iodine, green when it is rich in bromine, and blue when it is rich in chlorine.
The material is nevertheless highly sensitive and finds it difficult to change elements stably.
Kim’s team has however developed a simple technique to replace certain elements using nonpolar solvent and chemical additives.
“In the study, we added a nonpolar solvent, containing iodine (I), bromine (Br) and chlorine (Cl) to a solution of perovskite nanoparticles,” says Yung Jin Yoon, first author of the study. “Once the reaction takes place, the elements mixed within the nonpolar solvent switches its place with elements in original perovskite, which causes changes in luminescence.
The added chemical additive serve to separate the halogen element present in the nonpolar solvent.
As a result, the amount of halogen element in the solution increases, and over time, it is replaced with a halogen element in the conventional perovskite.
The researchers also succeeded in creating LEDs with red, blue, and green colors using perovskite nanoparticles made with this technology.
Image and content: UNIST