白光LED荧光粉涂敷工艺及光学性质

Promoting of the Phosphor-based White-LED and Optical Properties

在20mA电流下,对自行设计的白光LED进行测试,发现荧光粉远离芯片封装方法与传统封装方法相比,流明效率提高了20.3%。效率的提高主要是因为减小了LED芯片对荧光粉散射的吸收。同时测得随着正向电流的增加,色坐标x,y的值逐渐减小,色温升高,而光通量呈非线性增加,流明效率逐渐下降。

White light-emitting-diodes （LEDs） are known as a new generation lighting source. The luminous flux, color temperature and color rendering property are the three main index in light source. Using a blue LED with a phosphor layer which is excited by blue light and down-converting to the second light, such as yellow light, white light can be produced. Now white-LED is a hot-spot of research, the point of designing white-LED used for lighting is its colour temperature and efficience, and the phosphor layer in white-LED is very impor- tant to this. The placement of the phosphor, the geometry of the encapsulation dome, and the reflector cup in- fluence on the optical loss, and henqe on the device efficiency. We can find the energy loss term in the one- dimensional model and observe the phosphor layer thickness and boundary effect. Finally we can optimize the phosphor-type white LED package to obtain higher light extraction efficiency. Recently, it has been demon- strated that a large separation between the phosphor and the primary LED emitter, which we refer to as remote phosphor arrangement, enhances the phosphorescence extraction by reducing the optical power absorbed by the LED chip. The experimental enhancement of phosphor efficiency is 24% for blue-pumped yellow phosphor at 20 mA forward current. This improvement is mainly due to the reason：the phosphor-on-top arrangement re- duces absorption of phosphorescence the LED chip. it is not known what will happen to the yellow light when it strikes the phosphor medium. To the best of our knowledge, there are no past studies that have quantified the transmission and reflection properties of light outside the excitation wavelength region of YAG： Ce phos- phor. By analysing, the color coordinate, color temperature, Luminous flus, Lumen efficiency varied with for- ward current. From the result of the experiment,we know that color coordinate x and y is minish varing slowly with the increasing forward cureent. The color coordinate and the color temperature is the same uptrend. The luminous flux increases with increasing forward current, but the lumen efficiency decreases with increasing the forward current.