兩岸新能源研討會, 12rd Oct., 孫慶成 Ching-Cherng Sun 國立中央大學光電系

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1 兩岸新能源研討會, 12rd Oct., LED 固態節能照明 孫慶成 Ching-Cherng Sun 國立中央大學光電系 Department of Optics and Photonics/Institute of Lighting & Display Science National Central University, Chung-Li 320, TAIWAN Tel: , Fax: ccsun@dop.ncu.edu.tw 1

2 Location of NCU/DOP 2 2

3 History of DOP 年成立光電科學研究所 2006 年改制為光電科學與工程學系 Original Building New (Green Building)

4 中央大學光電系 / 照明與顯示科技研究所是您實現夢想及理想的推手 4 楊宗勳 陳彥宏 孫慶成李正中鄭益祥張正陽張榮森陳啟昌 欒丕綱 陳怡君陳昇暉戴朝義伍茂仁鍾德元孫文信梁肇文張殷榮陳思妤 張瑞芬 賴坤佑 4

5 Institute of Lighting and Display Science 5 照明與顯示科技研究所 Since Aug. 1st, 2008 The first lighting-related institute in Taiwan 台灣第一個照明科技相關系所 LED Solid-state Lighting Projection Display 3D Holographic Display Human Factors Optics Color Technology Photometry Laser Display Glare Vision 5

6 Motives of LED Lighting 6 Energy Efficient Efficiency LEDs up to 90% less energy Long Life LEDs last up to 100,000 hrs compared to 1000 for typical incandescent bulbs. Vivid Colors LEDs give pure saturated colors with up to 130% more color gamut compared to standard NTSC specifications. High Reliability LEDs ae solid state devices, no moving parts, no glass and no filaments to break. Environmentally Friendly LEDs contain no mercury, and are less disposal waste in the environment owing to long life. Increased Safety LEDs turn on faster, providing quicker response in applications like automotive brake lights. Multiple Applications 6

7 Illumination Requirement 7 7

8 Correlated Color Temperature 8 Warm White Cool White 8

9 How to Generate White Light 9 RGB Color Mixing -- High Color Gamut -- Excellent Color Tuning -- PWM or Others Control Blue-Die + Yellow Phosphor -- Easy and Simple -- Cost Effective -- High Efficiency UV-Die + RGB Phosphors -- High Color Gamut -- CCT Tuning with Phosphors -- UV Blocking and Damage 9

10 Progress in LED s Efficiency 10 Luminous Efficiency (lm/w) Electrical Discharge Lamps LED s World record Incandescents Fluorescen t Tungsten- Halogen LED ma 10

11 LED Efficiency Roadmap in Japan 發光效率 (lm/w) Cool White (H Eff) Cool White (H CRI) Warm White

12 LED 元年 :

13 13 Display Human Factor Cognitive Science Bio Lighting Agriculture JI Chyi, CC Chen, CY Liu, RS Liu, JY Chang, MJ Wu, TY Chung, TH Yang, CC SUN CC SUN, TH Yang, TY Chung, YC Chen, CY Liu, KY Lai, G Zissis, SY Chen, CH Chang, CC Chen, JI Chyi Color Phosphor Thermal Management Material Chip Processing Package Optics 色彩光學實驗室固態照明光學實驗室環測實驗室封裝與量測實驗室光電材料與元件實驗室 13 眩光與視覺評估實驗室光電與電子材料實驗室照明與顯示量測實驗室光電熱整合實驗室生醫光學影像實驗室

14 Photonic Recycling in LED SSL 14 Zero-order Optics 零階光學 Light Extraction First-order Optics 一階光學 Package Efficiency Second-order Optics 二階光學 Lens efficiency Third-order Optics 三階光學 Lighting Fixture, Glare 14

15 Precise LED Model 15 Near-field Light Emitter Mid-field (Light Pattern varies from a distance to another) Far-field (Fraunhofer region, light pattern does not vary) Ref : C. C. Sun, T. X. Lee, S. H. Ma Y. L. Lee and S. M. Huang, Optics Letters 31, (2006). Optics Optics of of Solid-State Lighting Lab., DOP,, NCU 15

16 Measurement vs. Simulation 16 Distance : 1 cm cm Relative Intensity (a.u.) NCC = 99.5% Measurement Simulation Angular displacement (Degrees) Ref.: W. T. Chien, C. C. Sun, and I. Moreno, Precise optical model of multi-chip white LEDs, Optics Express 15, (2007). Optics Optics of of Solid-State Lighting Lab., DOP,, NCU 16

17 Measurement vs. Simulation 17 Distance : 3 cm cm Relative Intensity (a.u.) NCC = 99.6% Measurement Simulation Angular displacement (Degrees) Ref.: W. T. Chien, C. C. Sun, and I. Moreno, Precise optical model of multi-chip white LEDs, Optics Express 15, (2007). Optics Optics of of Solid-State Lighting Lab., DOP,, NCU 17

18 Design of Multi-chip white LED 18 Real sample Optical model 4 chips inside Measurement Simulation LED + Reflector Divergent angle: 60 Optics Optics of of Solid-State Lighting Lab., DOP,, NCU 18

19 Importance of Phosphor Model 19 Blue Yellow Phosphor - Blue Chip Integration A good phosphor model can make an LED to perform consistent color performance enable small spatial CCT variation improve the yield rate of package optimize the luminous efficiency Optics Optics of of Solid-State Lighting Lab., DOP,, NCU 19

20 Modeling Procedure 20 Scattering modeling phosphor plate phosphor plate Absorption coefficient phosphor plate Bad Conversion Efficiency Successful phosphor model Good Verification with real LEDs Simulation Ref : C. C. Sun, C. Y. Chen, H. Y. He, C. C. Chen, W. T. Chien, T. X. Lee and T. H. Yang, Modeling the radiation pattern of LEDs, Optics Express 16, (2008). Optics Optics of of Solid-State Lighting Lab., DOP,, NCU Blue Yellow 20

21 Color Coordinate %-Exp 10%-Sim 15%-Exp 15%-Sim w/o Lens with Lens w/o Lens with Lens Ref : C. C. Sun, C. Y. Chen, H. Y. He, C. C. Chen, W. T. Chien, T. X. Lee and T. H. Yang, Modeling the radiation pattern of LEDs, Optics Express 16, (2008). Optics Optics of of Solid-State Lighting Lab., DOP,, NCU 21

22 Verification with Real Package 22 Concentration 10 % 15 % Package Type Simulation x=0.241 y=0.200 x=0.230 y=0.182 x=0.281 y=0.283 x=0.248 y=0.223 Measurement x=0.240 y=0.202 x=0.223 y=0.184 x=0.284 y=0.279 x=0.244 y=0.223 Deviation Δx= Δy= Δx= Δy= Δx= Δy= Δx= Δy= Ref : C. C. Sun, C. Y. Chen, H. Y. He, C. C. Chen, W. T. Chien, T. X. Lee and T. H. Yang, Modeling the radiation pattern of LEDs, Optics Express 16, (2008). Optics Optics of of Solid-State Lighting Lab., DOP,, NCU 22

23 Spatial CCT Uniformity 23 A good emitter generates consistent CCT for all viewing angles CCT (K) What we need rotated angle 23

24 Various CCTs 24 CCT Variation(Normalized to on axis value) Rotated angle (degree) 2800K 3000K 3500K 4000K 4500K 5500K 5700K 6500K CCT (K) Rotated angle (degree) 2800K 3000K 3500K 4000K 4500K 5500K 5700K 6500K 24

25 25 Introduction & Motivation 25

26 Efficiency Enhancement Photon Recycling 26 Photon-recycling is a way to effectively extract the backward lights and increase the optical efficiency

27 DBEF : Photon-recycling 27 27

28 Optics Approaches in LED SSL 28 Photon-recycling Effects Zero-level Optics 零階光學 Light Extraction First-level Optics 一階光學 Package Efficiency Second-level Optics 二階光學 Light pattern Third-level Optics 三階光學 Anti-Glare 28

29 29 Light Extraction through Photon-recycling 29

30 Light Extraction by Photon-recycling 30 No photon-recycling 30

31 Light Extraction : Roughening 31 By introducing a 2-D periodic structure in an interface between two materials with large refractive index difference 31

32 Light Extraction of LEDs 32 B=0 Inversed pyramid structure B=D Well structure Largest Smallest Ref : C. C. Sun, C. Y. Lin, T. X. Lee, and T. H. Yang, Enhancement of light extraction of GaN-based LED with introducing micro-structure array, Optical Engineering (Letters) 43, (2004). 32

33 Surface Texture in Thin-GaN 33 Reference: T. Fujii, Y. Gao, R. Sharma, E. L. Hu, S. P. Danbaars, and S. Nakamura, Increase in the extraction efficiency of GaN-base light emitting diodes via surface roughening, App. Phys. Lett. 84, 855, (2004) 33

34 Three Types of LED 34 P-GaN AlGaN MQW AlGaN N-GaN GaN Sapphire GaN P-GaN AlGaN MQW AlGaN N-GaN GaN Sapphire N-GaN AlGaN MQW AlGaN P-GaN Metal Substrate Wire-bonding Flip-Chip Wafer-bonding (Thin-GaN) 34

35 LEE by Cavity Photon-recycling 35 Absorption Coefficient = cm -1 Absorption Coefficient = 200 cm -1 Ref. : Optics Communications 284, (2011). Ref. : Optics Express 15, (2007). 35

36 36 Directionality Enhancement through Photon-recycling 36

37 Next-generation Display 37 Powerful Light Source Required Long life time (>20,000 hrs) To provide more saturated colors LED inside LED is expected to perform High directionality High injection power Low thermal resistance 37

38 Etendue vs. Flux 38 da S dω Etendue : a Geometric Factor Flux of an Arbitrary Source Flux of a Lambertian Source Flux =Φ= L cosθda dω= 2 Etendue ε n cosθdas d aperture = = Ω Flux = Φ= L( θ)cosθdas dω aperture Lamb. Lamb. S 2 n aperture L ε ε = n L 2 Φ Lamb 38

39 Directionality Enhancement 39 Optical system angle acceptance is 15 : 1.2 Lambertion type Directionality type 1.0 Intensity The same total power Angle (degree) Ref. : Luminus 39

40 Squeeze Etendue by PC Structure 40 Photonic Crystal (Diffraction Structure) through PC Structure LEE at small angle Etendue Ideal case : 100% light extraction (total flux by the active layer) Original case : Light extracted from the die 40

41 Angular Flux Utilization (AFU) 41 Larger AFU means more flux in a certain light cone but not for smaller etendue. Lager LEE means less lights absorbed in the LED so less heat is generated. 41

42 Through Micro-structure cm :142.4% 30 :190.5% 60 :263.3% 15 :439.1% 30 :423.6% 60 :404.3% 15 :259.5% 30 :312.4% 60 :464.1% 15 :107.4% 30 :114.0% 60 :116.6% 100% Ref. : J. Display Technology 7, (2011). 15 :305.4% 30 :305.8% 60 :370.0% 15 :366.5% 30 :362.6% 60 :435.7% 15 :252.6% 30 :253.6% 60 :273.3% 42

43 43 Lighting Cavity through Photon-recycling 43

44 LED Lighting with Low Glare 44 Better quality of LED illumination : Low-glare illumination Tunable planar light source Luminance & Color Uniformity Uniformity vs. Efficiency 44

45 High-efficiency Cavity with PR 45 Uniformity vs. Efficiency Larger Cavity Thickness Higher Efficiency Smaller Design Freedom Smaller Lower Larger 45

46 Volume-scatter Diffusers 46 R T : 55 % 60 % 70 % for one shot 46

47 Side Walls with High Reflectivity 47 I. Sliver Scatter sheet (R=82%) Cross section Random rough surface High reflective sliver-coating sheet II. White Scatter sheet (R=86%) Cross section White scatter sheet The high reflective sheet and white scatter sheet are usually used in BL! 47

48 Cavity Efficiency 48 Side wall Sliver Scatter sheet White scatter sheet 1 diffuser (E 1 ) 2 diffusers (E 2 ) 1 diffuser (E 1 ) 2 diffusers (E 2 ) D % (86%) 70.5% (72.9%) 89.5% (88.2%) 79.3% (76.2%) D % (84.3%) 69.4% (69.8) 88.4% (86.6%) 78.9% (73.1%) D % (79.2%) 63.4% (60.4) 86.0% (81.7%) 73.1% (63.6%) * Cavity size is cm 3. * 2 Diffusers : One is located on top of the Ref. Optics Express 18, (2010). cavity, the other is located at half of the height. * Light source : White LED. 48

49 Cavity Efficiency 49 E T Single diffuser = R R b Cavity Transmittance T70 T60 T55 95% Reflectance of side wall Ref. : Optics Express 18, (2010). 49

50 Beam Shaping x10 60 x26 80 x20 30 x5 60 x _lens array_case _lens array_case1 50

51 Optical Cavity in High-photon-recycle Rate 51 R=95% 51

52 52 What is True Efficiency? 52

53 Improvement of Lighting 53 Original Full Cutoff Source: 53

54 Light Pollution from Outdoor Luminaire 54 Direct up light Sky glow Upward reflected light Glare zone Wasted Energy Glare Spill light Light trespass Window Direct glare Useful light Source: NLPIP 54

55 True Efficiency : Optical Utilization Factor m 1.5 m 12 m 35 m Optical Utilization Factor (OUF) = Flux on Target Flux by Light Source 55

56 Street Light : What is true? 56 Luminous Efficacy (for luminaire) (>70lm/W) Optical Utilization Factor (for optical design) (>40%) Uniformity (for human factor) (>1/3) 56

57 57 57

58 58 Optics Optics of of Solid-State Lighting Lab., DOP,, NCU 58