| Phosphor-converted LED(pc-LED)is currently the most widely used white light acquisition scheme in industrial production.The pc-LED has shown the advantages of high lumen efficiency,low production cost,and mature technology.The phosphor is an important component in the conversion of white LEDs by phosphors.The increase in temperature will reduce the conversion efficiency and quantum efficiency of phosphors in pc-LEDs,and may also cause packaging materials to oxidize and to become yellow.Besides,it will shorten the device life.These will not only reduce the luminous efficiency of the LED,but also affect its light color quality,such as causing color coordinate shift.Therefore,it is becoming more and more important to accurately and quickly determine the temperature of the phosphor or phosphor/silicone mixture during the phosphor conversion in LED operation process and to study the effect of temperature on the surface of the phosphor/silicone mixture,which is also conducive to further doing research on optical and thermal properties of the pc-LED.Related technologies commonly used for temperature measurement of light-emitting devices in semiconductor such as LEDs can be mainly divided into three categories:contact,halfcontact,and non-contact.Contact measurement technology is to measure the surface temperature of LEDs by direct physical contact.Since this method directly contacts the chip surface,it is relatively easy to damage the LED device,and it is not suitable for the packaged LED device.The half-contact measurement technology mostly introduces some temperature-sensitive materials during temperature measurement.This method is easy to be interfered by the temperature-sensitive materials and affects the measurement results.Non-contact measurement technology is an indirect measurement method.It calculates the temperature by measuring a certain temperature-sensitive parameters of the LED device.This method avoids damaging the structure of LED device and the measurement is also relatively fast.The main work of this paper includes the following aspects:1、This paper proposes a non-contact temperature measurement method,that is,DNEP temperature measurement method.By dividing,normalizing and integrating the phosphor emission spectrum,the best temperature-sensitive parameters(TSP)are sought.Use the linear temperature dependence of this TSP to test the temperature of the phosphor on the surface of the packaged pc-LED sample.Measurement results are compared with those measured by the micro thermocouple and those of the LED chip,to prove the feasibility and reliability of the testing scheme and to explain the reason for the errors.We suggest that this proposed method can provide a useful tool for further study of optical and thermal characteristics in pc-LED.2、Conduct the two-dimensional temperature distribution test on the surface of LED phosphor.based on the DNEP method,combined with micro-hyperspectral imaging method,the temperature measurement scheme has been improved and upgraded,and the two-dimensional distribution testing of the phosphor temperature on the LED surface has been achieved.Measurement results are compared with those measured by the DNEP method and the micro thermocouple.Besides,the temperaturedependent optical characteristics of phosphors are also investigated in the micrometer scale.The advantages of this work include the following aspects:(1)The DNEP temperature measurement method is non-contact measurement and is not affected by LED device packaging.(2)The The experimental device is simple and easy to operate,suitable for fast online testing.(3)It can be combined with microscopic hyperspectral imaging technology to realize the two-dimensional distribution test of the surface temperature of the phosphor at the microscopic scale.It is believed that this detection method will cause great interest in the industry and academia in the field of lighting and display. |
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