LED light color light color regulation mechanism reveals

　　　　 When the LED illumination source is used for a long time, the brightness becomes dark and the color drift occurs. Recently, Associate Professor Chen Lei and Professor Jiang Yang of the School of Materials Science and Engineering of Hefei University of Technology revealed the scientific mechanism of this phenomenon in the yttrium aluminum garnet series LED fluorescent materials and their light color control mechanism, in order to further improve the performance of LED fluorescent materials. Provides an important means. The research results were published in the British "Nature" journal "Science Report".

Due to its high luminous efficiency and relatively good thermal stability, yttrium aluminum garnet phosphor is the most widely used phosphor in white LED device packaging. The white light of the LED using the phosphor is a cool color light, and the comfort is poor. In order to change the color of LED light from cold light to warm light, the commonly used method is to replace the ytterbium ion with ytterbium ions in the yttrium aluminum garnet phosphor, so that the emission wavelength of the phosphor is red-shifted, which can reduce the color temperature and improve the color rendering index. . However, the substitution of cerium ions for cerium ions results in a decrease in luminous efficiency and a deterioration in thermal stability. For this phenomenon, the classical positional coordinate model and the molecular orbital hybridization theory cannot be reasonably explained for a long time.

Chen Lei and his research group combined the electronic energy band structure, electronic state density and charge differential density theory calculation, from the electron cloud extrusion deformation angle in the rigid structure, the spectral red shift, strength drop and thermal stability caused by Gd ion substitution The poor intrinsic mechanism gives a new explanation: due to the large radius of Gd ions, the electron cloud extrusion deformation will occur in the rigid structure of yttrium aluminum garnet, crystal field enhancement, electron effective mass reduction, and electron spread energy level range. The enlargement and the band gap are reduced, resulting in a decrease in luminous efficiency and a decrease in thermal stability.

This theory not only scientifically explains the luminescence phenomenon of yttrium aluminum garnet phosphor after Gd substitution, but also has important guiding significance for the development of new rigid structure fluorescent materials. "Based on the model established by this theory, the future can also guide the development of artificial gemstone crystals with specific color, and give more colorful colors, such as various synthetic diamonds, sapphires and rubies." Chen Lei introduced.