The dominance of white LEDs as the main light source may soon come to an end with a new alternative that offers superior versatility.

photonic crystal or nano antennaIt is being developed as an advanced optical control technology, a two-dimensional structure with a periodic arrangement of nanoscale particles. Under the influence of light, its combination with a nanoantenna phosphor plate creates a harmonious combination of blue and yellow light.

White LEDs have been developed in the form of white laser diodes, or LDs, consisting of a yellow phosphor and a blue LD. Blue LEDs are highly directional, while yellow phosphors radiate in all directions causing unwanted color mixing.

To solve this problem, the researchers developed phosphor plates along with nanoantennas using aluminum metal, which provides enhanced photoluminescence. Aluminum nanoparticles effectively scatter light and improve the intensity and directionality of light; however, aluminum also absorbs light, reducing output. This is a major bottleneck, especially in high-intensity lighting systems.

Now, a research team from Kyoto University has achieved a tenfold increase in directional photoluminescence by replacing aluminum with a better material.

“Titanium dioxide seems to be a better choice because of its high refractive index and poor light absorption,” says lead author Shunsuke Murai.

Although the luminous intensity of titanium oxide initially seemed lower than that of metallic aluminum, the team used computer simulations to develop the optimal design for the nanoantenna.

“The new nanoantenna phosphors are advantageous for intensely bright yet energy-efficient solid-state illumination because they can suppress the temperature rise during irradiation,” Murai explains.

“In the process of finding the optimal sizes, we were surprised to find that the thinnest phosphors produced the brightest photoluminescence and showed how to increase direct emission intensity and overall performance.”