高显色白光LED的制备及其变温特性

Preparation and Temperature-Variation Properties of High Color Rendering Index LED

分别用黄色、红色荧光粉和黄色、红色、绿色荧光粉制备了两种高显色指数白光发光二极管(LED),调整荧光粉的比例使显色指数达到最高。对两种样品进行光学测试,发现加绿粉的样品光通量比较大,这是因为加绿粉后绿光成分较多,而绿光的视效函数比红光的大得多。对两种样品进行10℃～90℃的变温测试,发现发光效率都降低,显色指数反而升高。发光效率降低一方面是由芯片的内量子效率降低引起的,另一方面是芯片的发射波长红移使其与荧光粉的激发波长不匹配,并且荧光粉在升温时激发效率会降低。显色指数升高是因为高温时芯片发出的蓝光光谱变宽,使得整个光谱相对于室温时的光谱更平滑,更接近太阳光谱。

Two kinds of high color rendering index light emitting diode （LED） are made by yellow, red phosphor and yellow, red, green phosphor respectively. The light output of the sample with green phosphor is bigger due to more green light in spectrum after the addition of green phosphor and the larger vision function of green light than that of red light. The luminous efficiency decreases and color rendering index increases when the testing temperature varies from 10 ℃ to 90 ℃. This suggests that, besides the degradation of internal quantum efficiency, the mismatch of red shift of wavelength of the chip and the excitation wavelength of phosphor and the degradation of excitation efficiency of phosphor at high temperature are all the reasons of degradation of luminous efficiency. The color rendering index increases due to wider spectrum of blue light emitted by the chip at high temperature which makes the spectrum smoother and closer to the spectrum of the sun.