New technique brings colour tuning capabilities to LED bulbs

Researchers claim to have developed a new technique which could enable LED bulb to tune bright white and warmer colours at the same time.

The team demonstrated the possibility of colour tuning simply by changing the time sequence at which the current is provided to the device. Light-emitting diodes or LEDs are semiconductor devices that emit light when an electric current is passed through it.

Notably, the technique is compatible with current LEDs that are at the core of commercial solid-state LED lighting according to a study published in the Journal of ACS Photonics Funder.

In today's active LED displays, different colours are produced by three to four individual LEDs that are placed close to each other and create the different fundamental colours needed to produce the full-colour spectrum.

"We demonstrate that this can be achieved by a single LED. We show that is possible to attain red, green and blue emissions originating from just one GaN LED-structure that uses doping with a single type of rare earth ion, Europium (Eu). Using intentional co-doping and energy-transfer engineering, we show that all three primary colors can emit due to emission originating from two different excited states of the same Eu3+ ion (~620 nm and ~545nm) mixed with near band edge emission from GaN centered at ~430nm. The intensity ratios of these transitions can be controlled by choosing the current injection conditions such as injection current density and duty cycle under pulsed current injection," says researcher Dierolf.

In other words, the team achieved color-tunability in a single LED through the manipulation of the emission properties of an atomic-type dopant. According to Dierolf, this research may benefit those who are looking for more comfortable "warmer" white light from LEDs.

The materials used in previous research on color tunable LEDs did not allow for easy integration with current LED technology, he adds. This work is compatible with current GaN-based LEDs that are at the core of commercial solid-state LED lighting.