Research Progress Of Red Phosphors For White LEDs

At present,with the rapid development of science and technology,people's awareness of energy conservation and environmental protection has gradually increased.Against this background,white light-emitting diode?LED?as the new light source has become an inevitable choice for mankind to pursue a higher quality of life due to its many advantages,and has quickly occupied a place in the lighting market.The performance of white LEDs is closely related to the phosphors used.In particular,the traditional white LEDs composed of blue chips and yellow phosphor YAG:Ce³⁺ have the problems of poor color rendering and cold color due to the lack of red light components,which limits to promote its use.Whether it is used for blue light excitation to supplement red light components,or as one of the three primary color phosphors excited by ultraviolet light,red phosphors have shown great importance.In order to improve the usability of red phosphors in white LEDs,scholars have conducted a lot of research in recent years.This article taking red phosphor as the research object,systematically discusses its research progress from three aspects,analyzes and summarizes it in conjunction with related research work,and finally puts forward the prospects.The specific contents are as follows.First of all,according to the two categories of dry chemical method and wet chemical method,several common preparation methods of red phosphors are introduced,including basic principles and process steps,etc..Combined with specific examples,the effects of different process parameters in each method on the luminescence performance of the prepared phosphor and the scheme for optimizing the synthesis conditions were discussed.By comparing the differences in the morphological size,luminous intensity and color rendering index of the materials obtained by different methods,the advantages of each method are analyzed and summarized,and the existing problems are pointed out.In addition,the new preparation method and the fusion aid between different methods are also introduced.Secondly,taking the red phosphor system as a division,it focuses on the major hosts commonly used in red phosphors.Comprehensive research at home and abroad,the work done on improving the existing and developing new hosts for red phosphors was detailed.The crystal structure of different systems of red powder and the luminescence characteristics of the activated ions used are briefly described,and the advantages and disadvantages of each host are given.It also pointed out that there is still room for further improvement in the matching performance,color rendering and quantum efficiency of the existing red phosphor.Finally,the method of optimizing the luminous performance of the red phosphor was explored from three aspects.The energy transfer effect between luminescent ions and the co-doping of non-luminescent ions on the emission spectrum of the material,the effect of charge compensation on the compensation of lattice defects and the improvement of internal quantum efficiency,and the positive effect of surface coating on the enhancement of moisture resistance and thermal stability for red phosphors are introduced respectively powder's.