Fabrication And Characteristics Studies Of White LEDs With Low Color Temperature And High Rendering Index

With the development of semiconductor technology and packaging technology, semiconductor light source which was used for display and instructions has been used in lighting application which put forward higher requirements for the white LED's color rendering and color temperature.Our research focused on the packaging technology of white LED with high color rendering and low color temperature by the excitation of blue LED chip with YAG yellow phosphors, and red phosphors and green phosphors. And the light color properties of high color rendering and low color temperature white LED were also studied with different electric parameters as well as the aging properties in different environment. The results show that the electric current has littile influence on the color coordinates of small power white LED, and the electric current has little influence on the color rendering and color temperature of high color rendering and low color temperature white LED.The luminous flux increases with the increasing electric currentwhile the luminous efficiency decreases with it. In the early aging, luminous flux and luminous efficiency will slightly riseat first, and later it will decrease. With the increase of aging time, the main wavelength will slightly decrease,while the colour temperature will rise slowly.Analysis shows that the lumens reduction is mainly due to the aging of the phosphor and packaging material.