LED Lighting New Possibilities in the Future Carsten Dam-Hansen, Anders Thorseth, Dennis Corell, Peter Jensen, Søren S. Hansen, Haiyan Ou, Peter Poulsen, Roza Shirazi and Paul Michael Petersen. DTU Fotonik Technical University of Denmark 4000 Roskilde, Denmark pape@fotonik.dtu.dk
Light emitting diodes (LEDs) In the talk today I will discuss how LEDs in the future may contribute to: Energy savings and reduced CO2 emission Improved health Reduced stress Improved leaning Emotional excitement.
LED lighting: perspectives Solid state lighting with diodes increased in power level (within last 3-5 years) the future s lighting technology LED efficiency doubled every 3 years LEDs most efficient light source
Perspectives of light emitting diodes (LEDs) The most efficient diodes today have efficiencies around 130 Lumen/W (emitted light per W), incandescent light 8-12 Lumen/W. Today LED light sources have efficiencies around 125 Lumen/W. The lumen (symbol: lm) is the SI unit of luminous flux, measure of the power of light perceived by the human eye Paul Michael Petersen, Light Emitting Diodes
Future Perspectives of Light Emitting Diodes In the future lighting based on LEDs will be: 20 times more efficient than incandescent lighting 4-5 times more efficient than compact fluorescent tubes
COMPARISON WITH OTHER LIGHTING TECHNOLOGIES
Compact Fluorescent Lamps 4 00 450 500 550 600 650 700 Wavelength Bølgelængde in nm [nm] Compact Fluorescent lamps provide low color rendering but also low initial cost in comparison with LED lighting Paul Michael Petersen, Light Emitting Diodes
Incandescent bulb (Edison 1879) Paul Michael Petersen, Light Emitting Diodes
Incandescent bulb (spectral content) Paul Michael Petersen, Light Emitting Diodes 400 450 500 550 600 650 700 Wavelength Bølgelængde [nm] [nm] Incandescent lamps provide high color rendering but also low initial puchase cost in comparison with LED lighting
The basic mechanism of LEDs emitted light n-type - - - - - - + - - -+ + + p-type + + + - + + Energy of electrons electron Conduction conduction band band gap valence band light emission - V + hole The basic mechanism of an LED involves the spontaneous emission of photons via the radiative recombination of electron hole pairs, which converts the electrical energy into optical radiation. Paul Michael Petersen, Light Emitting Diodes
Light quality from LEDs Paul Michael Petersen, Light Emitting Diodes
What are the obstacles to shape the future of lighting? Paul Michael Petersen, Light Emitting Diodes
LED lighting quality program The aim is to establish a transparent overview of light quality and energy efficiency of SSL product available on the market. - is a R&D project financed by ELFORSK (PSO 342-035) - headed by DTU Fotonik in collaboration with Statens Byggeforskningsinstitut Dansk Center for Lys and Energirådgiveren DANLED, RAFA LYS, Lumodan, Dioder-Online, Flash Light and LED-TEK Paul Michael Petersen, Light Emitting Diodes 13
LED lighting quality program Defined quality parameters - Power [W] - Luminous flux [lm] - Correlated color temperature [K] - Color rendering index 266 SSL products have been tested: Voltage [V] Directional Non directional 230 95 49 12 99 23 Paul Michael Petersen, Light Emitting Diodes 14
LED lighting quality program Measurement results, luminous efficiency for non-directional lamps Paul Michael Petersen, Light Emitting Diodes 15
LED lighting quality program Measurement results, luminous efficiency for directional lamps (based on total flux) Paul Michael Petersen, Light Emitting Diodes 16
LED lighting quality program Measurement results, lumen maintenance as an indication of lifetime 94 82 % of initial flux after 10500 h operation (use to extrapolate) 3 observed sudden faliures of 48 samples Paul Michael Petersen, Light Emitting Diodes 17
LED lighting quality program Conclusion Many LEDs products with too low efficiency and poor color rendering Insufficient product information High initial purchase costs Further work User preference test at Sbi Participation in IEA 4E Solid State Lighting Annex New strict test method has been published IEA 4E SSL 2013 Interlaboratory Comparison part of our EUDP project: Test og standarder for SSL produkter - IEA-4E-SSL Paul Michael Petersen, Light Emitting Diodes 18
LED lighting quality program Demonstration of LED list: Effektforbrug 60 W 800 lm Måles i W Lysstrøm angiver det samlede lys fra en pære Måles i lumen lm Ra-indeks beskrives lyskildens evne til at gengive farve i forhold til en reference lyskilde Ra = 100 Perfekt farvegengivelse Jo mindre end 100 des dårligere Farvetemperatur beskriver en lyskildes hvide farve, fra varm til kold hvid. Måles i grader Kelvin [K] Lystrøm Effektforbrug Ra-indeks Farvetemperatur [lm] [W] [K] Produkt 1 902 12 75 2750 Produkt 2 850 11 90 3012 Produkt 3 450 7 82 3025 Produkt 4 250 5 85 3500 Produkt 5 200 4 96 6450 Paul Michael Petersen, Light Emitting Diodes 19
Nanotechnology will give us new possibilities in the future
GaInN UV Light Emitting Diodes Layer structure of GaInN UV LED grown on sapphire substrate emitting at 370 nm
New Quantum dot technology LEDs with phosphorescent materials Hybrid LEDs based on Quantum dots Phosphorescence Blue luminescence e h hn2 FT hn1 Phosphor Today most white light LED sources use phosphorescent materials like YAG:Ce that is illuminated by a blue LED. The quantum dots are made of semiconductor materials and they work similar as the phosphorescent materials but they allow a more detailed control of the emitting wavelength and improved color rendering Paul Michael Petersen, Light Emitting Diodes
CdSe quantum dots Wavelength (nm) Photoluminescence spectra of CdTe quantum dots of various sizes. Different sized quantum dots emit different color light due to quantum confinement
Application of Photonic crystals(pc) in LED Coupling light from LED to waveguide for novel applications of light mixing In todays technology we have low coupling efficiency due to NA mismatch betewen LED and waveguide Paul Michael Petersen, Light Emitting Diodes
New possibilities with LED lighting in the future
Can light in the future improve human health?
Future lighting at hospitals Can light in the future improve human health at hospitals? Hostpital rooms facing east Hospital rooms facing west average length 19.80 days average length 23.47 day Morning sunlight reduces length of hospitalization Benedetti F. et al, Journal of Affective Disorders 62 (2001) 221-223
Light therapy Light therapy can be an effective treatment for mood disorders suggesting that light is able to affect mood state in the long term
EVIDENCE FOR A NOVEL PHOTORECEPTOR A few years ago it was found that the retina has a certain type of cells that when illuminated stimulate production of hormones in the pineal gland Melatonin and serotonin are very important for the human health and the human daily rhythm High Power LEDs, Paul Michael Petersen
Melatonin Melatonin has demonstrated to strengthen the immune system, and is today among researchers broad consensus that an increased incidence of Melatonin plays an important role in fighting cancer Melatonin is a powerful antioxidant that neutralizes harmful free radicals Melatonin increases the absorption of other antioxidants such as C and E vitamins Melatonin stimulates a number of antioxidants and enzymes Melatonin have a certain anti-inflammatory effect Melatonin activates the immune system's T lymphocytes (white blood cells)
Visual and non visual ganglion cell
Melatonin suppression versus lux Kilde: Mariana G Figueiro, Mark S Rea* and John D Bullough, Does architectural lighting contribute to breast cancer?, Journal of Carcinogenesis 2006
Melatonin suppression in humans 400 450 500 550 600 650 700 Bølgelængde [nm] (G.C. Brainard et al. J. Neurosci. 21 (2001) 6405-6412) Wavelength [nm] 4 00 450 500 550 600 650 700 Bølgelængde [nm]
White light from light emitting diodes Conventional white LED RGB -technology Spectral design and high light quality Miljøvenlighed lang levetid 400 450 500 550 600 650 700 wavelength Bølgelængde [nm] Blue diodes with phosphorescent materials 400 450 500 550 600 650 700 Bølgelængde wavelength [nm] High CRI-value > 90 and high efficiency adjustable color temperature Bølgelængde [nm]
NoBlue fra DTU Fotonik (No light below 440 nm) NoBlue har en god farvegengivelse og har forholdsvis lille melatoninundertrykkelse.
Claus Bjørn Larsen/Rockphoto How does light affect the emotional centers in the brain? Claus Bjørn Larsen/Rockphoto What colors and what spectral distribution of the light lead to the highest emotional excitement for the audience at rock concerts?
Brain activity related to emotional excitement The amygdala is associated with fear responses and pleasure. The hypothalamus links the brain to the hormone system and controls the circadian cycles The hippocampus is part of the limbic system that is associated with emotions
White light from light emitting diodes 400 450 500 550 600 650 700 Bølgelængde [nm]
Claus Bjørn Larsen/Rockphoto How does light affect the emotional centers in the brain? Claus Bjørn Larsen/Rockphoto You can tailor emotional excitement!
Conclusion We consider LED Solid state lighting with diodes the future lighting technology Our research show that it is possible to spectrally design new LED light sources that can replace incandescent bulbs and introduce significant energy savings. Moreover, in the future LEDs may improve: Improve health Emotional excitement. Learning Reduce stress for people living in our society.