Researchers at the solid state lighting and energy center (sslec) at the University of California, Santa Barbara, announced a breakthrough study to improve phosphors and make LED lighting brighter and more efficient. The researchers say their goal is to achieve 90% light efficiency, or 300 lumens / watt.

The researchers who jointly carried out this breakthrough research include ram Seshadri, a professor in the Department of materials and the Department of chemistry and biochemistry at the University of California, Santa Barbara, Steven denbaars, a professor of materials science, and jakoah brgoch, a postdoctoral associate researcher.

Seshadri said that the new development of solid-state lighting is gallium nitride LED. This technology is largely due to Shuji Nakamura, a professor of materials science at the University of California, Santa Barbara, who invented a high brightness blue LED. In solid-state white lighting technology, phosphors are applied to LED chips in such a way that photons emitted from blue gallium nitride LEDs pass through the phosphors, mixing the blue light into light in the green yellow orange range. When it is evenly combined with blue light, green yellow orange light will emit white light.

The preparation of phosphor materials is more like an art than a science - the crystal structure acts as the main body to activate ions, transforming high-energy blue light into low-energy yellow / orange light. "So far, there has been no complete explanation of what makes some phosphors effective and others ineffective. In some not so good crystals, some photons will always turn into heat and waste," Seshadri said

"Very few phosphor materials maintain their luminous efficiency at elevated temperatures," brgoch said. "Few people know how to select crystals to make fluorescent materials more effective and maintain light efficiency when the temperature rises.

However, using the calculation based on density functional theory, researchers determined that the rigidity of crystal structure is the key factor affecting the efficiency of phosphors, that is to say, a good phosphor needs to have a high rigid crystal structure. In addition, the index of structural stiffness can be calculated by density functional theory, so the phosphor can be screened first and then used. This breakthrough discovery provides a "fast lane" for high luminous efficiency and high brightness LED lighting. The elimination of inefficient incandescent and fluorescent bulbs is further accelerated.

"Our goal is to make LEDs achieve 90% light efficiency, or 300 lumens / watt, while the data we currently obtain in the laboratory is 60%. The light efficiency of incandescent bulbs on the market is about 5%, and fluorescent lamps are slightly higher, about 20%." Said den Baars, Professor of electronic and computer engineering and co director of sslec.