Solid-state lighting

Transcription

1 Solid-state lighting

2 Lighting prerequisite of human civilization 500,000 years ago- first torch 70,000 years ago first lamp (wick) 1,000 BC the first candle gas lighting 1784 Agrand lamp - the first lamp relied on research (Lavoisier) Limelight - solid-state lighting device 1876 Yablochkov candle 1879 Edison bulb Agrand lamp Limelight Yablochkov candle (1876) Edison bulb (1879)

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5 High Brightness LED Process Chain Keys for High Light Efficiencies Metal Organic Vapor Phase Epitaxy Chip Technology Package Epitaxy Internal Q. efficiency Light extraction Electr. losses Heat dissipation Light extraction (l-conversion + Stokes losses) Substrate Wall plug =... int electr extr package.

6 Front Emission of Today's Power LEDS Sapphire-PowerLED (generic) volume emitter top or bottom contacts Thinfilm Technology surface emitter top and bottom contacts ~ 49 % top emission Side emission > 97 % Thinfilm technology has the best front emission, higher luminance and best scalability.

7 ThinGaN: The Way to Improve Light Extraction Thinfilm principle: Present actions: prevent absorption in substr. highly reflecting mirror PowerThinGaN low internal absorption LED structure: thin epi layers prevent waveguiding optimize surface roughness contact textured surface 1mm QW GaN ^ Mirror layer Solder layer Carrier substrate PowerThinGaN; scematic side view PowerThinGaN top view Light extraction of 75% is reached

8 LED technology: solutions for white light chromaticity diagram 1st approach: Muli-colour-LEDs: InGaN E 560 Planck InGaAlP colour on demand turnable colours within the yellow triangle & white 2nd approach: conversion: blue LED + = yellow phosphorous white light

9 Chip Level Conversion (CLC): Principle improved light conversion chip level conversion (CLC) layer phosphor ThinGaN CLC ThinGaN CLC LED package excellent color homogeneity die sorted white chips high luminance Blue chip Yellow phosphor nm perfectly suitable for optical systems

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18 Lumen (lm) Unità di misura del flusso luminoso. Equivale al flusso luminoso emesso da una sorgente isotropica di intensità luminosa di 1 candela su un angolo solido di 1 steradiante Una sorgente isotropica con intensità luminosa di 1 candela emette un flusso luminoso totale di 4 lumen

19 Candela (cd) Unità di misura dell intensità luminosa Una candela è pari all'intensità luminosa, in una data direzione, di una sorgente che emette una radiazione monocromatica di frequenza pari a hertz e di intensità radiante in quella direzione di 1/683 di watt per steradiante

20 Dez. 98 Dez. 99 Dez. 00 Dez. 01 Dez. 02 Dez. 03 Dez. 04 Dez. 05 Dez. 06 Dez. 07 Radiant [mw] InGaN (Blue) Improvement Over Last 6 Years int ~ 73% ma Standard ATON int ~ 33% extr = 50% ThinGaN extr ~ 75% int ~ 30% extr = 25% 5 0

21 WPE [%] Fe [mw] efficacy [lm/w] Blue 300 µm class ThinGaN in 5mm radial package White 70% 60% 50% 40% 30% 20% 10% 0% WPE 440 nm) 58% 20 ma 31,4 mw current density [A/cm2] Latest achieved R&D record values efficacy 138 lm/w ca 8000K ca K ca K ma current density [A/cm2]

22 76% 84% 75% 94% 60% 84% 23% 77% Elect. Intern. Q.E. Extrakc. Eff. Package Conversion Stokes Lum. Flux white [lm] Power Balance of a White Power LED (1W Dragon) with 1mm 2 InGaN-Chip (today) mw lm/w can be reached with white Power LEDs today!!! 350 ma ; 3,2 V 67 lm/w Heat 75 lm Light lm/W Package 50% extraction electrical 75 lm Current [ma] Lum. Efficiency [lm/w] 80 Conversion mw

23 Further brightness improvement: approaches Increase current more lumens 1 st approach: Constant chip size - increase current density more lumens but less efficiency 2 nd approach: Constant current density - increase chip size more lumens but more costs

24 F v (lm) - White Further brightness improvement: increase current density 1mm x 1mm: with CLC Dragon with lens lm/W 84lm/W 94 lm 50% 50% 120 Phi_v (lm) efficiency (lm/w) lm R&D values; Dragon with lens 20 efficacy (lm/w) current (ma) lumen output saturates & efficacy drops with increased current reasons: non-linearity of IQE by 1) current density and 2) heating Dispositivi Optoelettronici

25 efficiency [a.u.] Technology platform efficiency of light generation dependent on current density: 1,4 1,3 1,2 1,1 1,0 0,9 0,8 0,7 epitaxy characteristic current density [A/cm2] 250 µm: 45,5 A/cm 2 rectangular: 27,8 A/cm µm: 81,2 A/cm 2 1 mm: 45,1 A/cm µm: 42,7 A/cm 2 comparison rectangular standard : Up to 15 % brightness increase by reduced current density Dispositivi Optoelettronici

26 F v (lm) - White efficiency (lm/w) PE[mW] EXT QE High End Chip Performance (R&D) 40 55% 47% 60% standard chip size % 40% V f = 20mA mW 30% 20% 10% % lm/w Phi_v (lm) efficiency (lm/w) Operating current [ma] lm 92,7 lm Dragon with YAGaG volume casting and spherical lens Current (ma) power chip 1x1mm² V f 350mA Lowest V f reported For power devices Dispositivi Optoelettronici

27 Further brightness imrovement: approaches Increase current more lumens 1 st approach: increase constant chip area challenges: - improve heat management (decrease R th of entire device) - improve linearity of IQE regarding current density 2 nd approach: increase constant current density increase chip area challenges: - decrease costs per chip area and package Dispositivi Optoelettronici

28 F v (White) [lm] Further brightness imrovement: increase chip area Single emitter with ThinGaN chips in OS packages at constant current density (50 A/cm 2 ) 1170lm OSRAM (50 lm/w) (> 80 lm/w) (82 lm/w) µm 6x 1000µm 1000µm µm 500µm 4x 1000µm 230µm 1 1,E+04 1,E+05 1,E+06 1,E+07 1,E+08 Active area (µm x µm) Coming soon: typ. 1000lm white light product

29 electrooptical efficiency [lm/w] Comparison of LEDs with conventional light sources CLC-LED 50 A/cm 2 RGB-LED 50 A/cm 2 OSRAM-OS LEDs: j < 10 A/cm 2 & realistic future products (< 2 j > 50 A/cm 2 glow discharge fluorescent halogen conventional light sources incandescent

30 Roland Haitz s Battlefields for LED Lighting and Our OSTAR Position 1,E+05 1,E+04 Flux/Lamp & Cost/Lumen (Red & White) OSTAR White 1,E+03 1,E+02 1,E+01 1,E+00 1,E-01 1,E-02 Cost/Lumen ($/lm) Red +20x/Decade Lighting Flux/Lamp (lm) -10x/Decade Battlefields for Lighting 1,E

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