This color palette consists of samples of various lanthanide nanocrystals that glow when excited with electricity. These are synthetic crystals that contain rare earth ions from the lanthanide element group. The electricity is converted into light. Depending on which lanthanides are involved, they glow in a different color of the visible light spectrum. This makes it easy and precise to control their appearance.
Lanthanide nanocrystals are known to be chemically stable and durable, producing clear, pure colors. However, these rare metals are non-conductive insulators and are therefore notoriously resistant to electrical excitation. But a research team led by Jing Tan from Heilongjiang University in China has now managed to get electricity to flow through this stubborn material.
To do this, the researchers used a trick: They wrapped the insulating nanocrystals in specially developed organic semiconductor molecules and applied electricity to them. The shell layer then captured the electrons and holes and transferred their energy to the lanthanide ions inside the crystal. These rare earths then began to glow. Spectroscopic studies showed that this energy transfer from outside to inside works very efficiently.
To get the desired color, all that was needed was to replace the lanthanide material: terbium ions (Tb3+) have a light green luminescence, europium ions (Eu3+) glow intensely red and neodymium ions (Nd3+) in the visible and near infrared range. By combining the ions or changing their concentration in the crystal, the natural color spectrum can be expanded. The technology now makes it possible to develop new components for electronics, such as displays, wearable devices, sensors and quantum computers.