정보통신프로젝트 Influence of the Size of a Phosphor Particle on Color Characteristics of a White LED Dong-hyun Lee, Sun-hong KIM (School of Information & Communication Eng.) Inha University (Advisor: Prof. Seung Gol Lee)

정보통신프로젝트 Contents 1. Research Purpose 2. Method of Research 3. Introduction 4. Main Subject 1) Optical Constants using MATLAB 2) Dependence of Light Scattering Intensity 3) Simulation using LightTools Program TM - Powder type Model - Remote type Model - Modified Model 5. Conclusion 6. Reference 2/21

정보통신프로젝트 Research Purpose As the size of a phosphor particle is varied, its optical properties change, and thus this tendency results in changing color characteristics of a white LED. Color Uniformity will influence the actual illumination effects and results in comfort for eyes. In order to increase the quality of LED, We check the size-dependent color characteristics and make the high quality White LED with other properties. 3/21

정보통신프로젝트 Method of Research Calculate the optical constants of phosphor particle based on Mie theory. Verify the calculated results by comparing them with optical constants reported in several papers. Define several white LEDs with different phosphor particles for simulating the LEDs with LightTools program TM. Analyze the emitting and color characteristics of several white LEDs and make the optimal model. 4/21

정보통신프로젝트 # Term definition A yellow to blue ratio (YBR) The YBR was defined as, were the light flux of yellow light and blue light incident on the receiver. Angular Color Uniformity (ACU) The ACU is defined as the ratio of minimum YBR to maximum YBR in the whole radiation angle from 0 to 180. Introduction 5/21

정보통신프로젝트 #Mie theory Mie theory has no size limitations and converges to the limit of geometric optics for large particles. Mie theory describes the scattering of electromagnetic radiation by a sphere. Introduction 6/21

정보통신프로젝트 Introduction 7 /21 Scattering Matrix Extinction Efficiency Scattering Efficiency Absorption Efficiency Expansion Coefficient

정보통신프로젝트 Total scattering & absorption coefficient 8 /21 Total scattering coefficient The increase of phosphor particle size, the scattering coefficients witness a trend of decrease. The increase of phosphor particle size, the absorption coefficients witness a trend of decrease, too. Optical Constant using MATLAB 15 um Total absorption coefficient

정보통신프로젝트 Dependence of Light Scattering Intensity 9 /21 50 um 1 1 um Polar graph 15 um Intensity

정보통신프로젝트 Simulation using LightTools Program TM 1*1 bottom radius: mm Height : mm 0.37 upper radius: mm LED chip :1Watt Silicon gel Encapsulation With powder phosphor Reflector cup # Conventional Powder Phosphor Model 10 /21

정보통신프로젝트 Simulation using LightTools Program TM (Volume(r 3 ) ∝ 1/Density) Radius1um15um50um Density (1/mm 3 )6.75 X , Mean-free path (mm) # Simulation Parameter 11 /21

정보통신프로젝트 Simulation using LightTools Program TM #Color simulation per radius R=1um R=15um R=50um 12 /21

정보통신프로젝트 Simulation using LightTools Program TM Radius1um15um50um Density (1/mm 3 )36.5 X ,0002,800 Mean-free path (mm) # Simulation Parameter 13 /21

정보통신프로젝트 Simulation using LightTools Program TM #Color simulation per radius R=1um R=15um R=50um 14 /21

정보통신프로젝트 YBR & ACU according to Radius YBR of angle(-80~80) ACU per radius 1um->15um : 19.8% reduction 15um->50um : 29.3% reduction 1um->50um: 43.3% reduction 15 /21

정보통신프로젝트 Simulation using LightTools Program TM Remote phosphor Radius: 1.8mm Height: 0.4mm # Conventional Remote Phosphor Model 16 /21

정보통신프로젝트 YBR & ACU according to Radius YBR of angle(-80~80) ACU per radius 1um->15um : 44.2% reduction 15um->50um : 13.5% reduction 1um->50um: 51.7% reduction 17 /21

정보통신프로젝트 New Model of Remote Phosphor Concave lens Remote phosphor Radius: 1.8mm Height: 0.4mm 1mm 0.1mm # Modified Remote Phosphor Model 18 /21

정보통신프로젝트 YBR and ACU in Standard and Modified LED Package standard Modified ACU: > ACU was improved about 50.5% 19 /21

정보통신프로젝트 Conclusion Radius Size Increased v Optical constants Incresed ↑ Scattering ratio decreased ACU decreased Radius Size Increased Reflectance ratio increased Incidence, Excitation ratio in phosphor increased Scattering ratio decreased In remote phosphor In conventional powder phosphor New model ACU increased 20 /21

정보통신프로젝트 Reference [1] Hoo Keun Park, Ji Hye Oh, and Young Rag Do, "Toward scatter-free phosphors in white phosphor-converted light-emitting diodes.“ Opt. Express 20(23), , [2]Kai Wang, Dan wu, Fei chen, Zongyuan Liu, Xiaobing Luo,and Sheng Liu,”Angular color uniformity enhancement of white light-emitting diodes integrated with freeform lenses” Optic letters,Vol.35,No.11,June 1,2010 [3] R. Hu, X. B Luo, H. Feng, and S. Liu, “Effect of phosphor settling on the optical performance of phosphor converted LED”, Journal of Luminescence, vol. 132, , [4] Zhu Y, Narendran N. J Light Vis Environ 2008;32:2. [5] W.-H. Chao, R.-J. Wu, and T.-B. Wu, “Structural and luminescent properties of YAG:Ce thin film phosphor,” J. Alloy. Comp. 506(1), 98–102 (2010). [6] Huai Zheng, Xing Fu, Run Hu, Sheng Liu and Xiaobing Luo,”Angular color uniformity Improvement for Phosphor-converted White Light-Emitting Diodes by Optimizing Remote Coating Phosphor Geometry” International Conference on Electronic Packaging Technology&High Density Packaging,2012 [7] Run Hu,Xiaobing LUO,Huai ZHENG,Sheng LIU,”Optical Constants study of YAG:Ce phosphor layer blended with SiO2 particles by Mie theory for white light-emitting diode package”,Front. Optoelectron, , /21

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