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Future of Lighting : LEDs, OLEDs, and Lighting Systems (and some lasers)
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Future of Lighting : LEDs, OLEDs, and Lighting Systems (and some lasers)

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Scientists and engineers continue to find new materials that better exploit the phenomenon of electroluminescence. These materials have higher luminosity per Watt, often lower costs per lumen, and …

Scientists and engineers continue to find new materials that better exploit the phenomenon of electroluminescence. These materials have higher luminosity per Watt, often lower costs per lumen, and thus increase the chances that light emitting diodes and organic light emitting diodes will begin to diffuse. Other advantages for them such as flexibility and size also increase the chances that they will diffuse. Furthermore, laser diodes also continue to experience improvements as scientists and engineers find new materials and reduce the size of the relevant features, thus increasing the number of applications for them.

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  • We start with existing forms of lighting and displays and move towards new forms of lighting and displays
  • There are severe limitations in the fundamental design of incandescent lights
  • There are also severe limitations in the fundamental design of fluorescent lights
  • We start with existing forms of lighting and displays and move towards new forms of lighting and displays
  • Different materials have been developed for different colors of semiconductor LEDs
  • Semiconductor LEDs now have higher luminosity per watt than do incandescent lights and will soon pass those of fluorescent lights
  • Creating a white LED had been a challenge, but one that has now been overcome
  • The U.S. Department of Energy thinks that we are still a long way from reaching the limits for luminosity per Watt (about 100 now)
  • Here is another look at expected improvements in luminosity per Watt
  • The cost of semiconductor LEDs are also falling at a rapid rate and thus will likely displace both incandescent and fluorescent lights
  • Costs fall as individualLEDs are made smaller and their wafers are made larger. This is another example of geometric scaling
  • This was the smallest in 2007
  • The U.S. Department of Energy believes that the price of LEDs will continue to fall
  • We start with existing forms of lighting and displays and move towards new forms of lighting and displays
  • LEDs can also be made from organic materials, which are often easier to process than semiconductor materials. Semiconductor materials require high temperatures, which leads to a need for expensive furnaces and other equipment. Scientists and engineers have been improving the luminosity per Watt for many years. Although the first OLED product was released in 1998, the market for them is still very small.
  • Will OLEDs eventually replace LEDs for lighting? Will OLEDs be used in other applications before they are used in lighting? What might these applications be?
  • Will OLEDs eventually replace LEDs for lighting? Will OLEDs be used in other applications before they are used in lighting? What might these applications be?
  • Will OLEDs eventually replace LEDs for lighting? Will OLEDs be used in other applications before they are used in lighting? What might these applications be?
  • We start with existing forms of lighting and displays and move towards new forms of lighting and displays
  • Improvements in semiconductor lasers have occurred in parallel with improvements in semiconductor LEDs
  • We start with existing forms of lighting and displays and move towards new forms of lighting and displays
  • We start with existing forms of lighting and displays and move towards new forms of lighting and displays
  • Transcript

    • 1. A/Prof Jeffrey Funk Division of Engineering and Technology Management National University of Singapore
    • 2. Source: Roland Haitz, Jeffrey Tsao, Solid-state Lighting: The case 10 years after and future prospects, Phys. Solidi A 208 (1): 17-29, 2011 What do Continued Improvements in Luminosity per Watt for LEDs Mean for Lighting?
    • 3. What about Organic LEDs (OLEDs) What do Continued Improvements in Luminosity per Watt for OLEDs Mean for Lighting? Source: Sheatset al, 1996, Organic Electroluminescent Devices, Science 271 (5277): 884-888 and ChangheeLee’s presentation slides; PPV: poly (p-phenylenevinylene)
    • 4. Session Technology 1 Objectives and overview of course 2 When do new technologies become economically feasible? 3 Two types of improvements: 1) Creating materials that better exploit physical phenomena;2) Geometrical scaling 4 Semiconductors, ICs, electronic systems, big data analytics 5 MEMS and Bio-electronics 6 Lighting, Lasers, and Displays 7 Information Technology and Land Transportation 8 Human-Computer Interfaces, Biometrics 9 Superconductivity and Solar Cells 10 Nanotechnology and DNA sequencing This is Sixth Session of MT5009
    • 5. Outline Existing state of lighting Light emitting diodes (LEDs) Organic light emitting diodes (OLEDs) Laser Diodes Applications for Laser Diodes Bioluminescence
    • 6. Type of Specs Incandescent Lamp Fluorescent lamp LED OLED Thickness VeryThick VeryThick 6.9 mm (for LED TV) 1.8mm Flexibility Veryinflexible, and breakable Veryinflexible, and breakable Some flexibility Most flexible Danger to eyes Can’t stare at them Can’t stareat them Can’t stare at them Okaytostare Lifespan 500-700 hrs >10, 000 hrs 100, 000 hrs 15, 000 hrs Price of 60 Watt bulb <1 USD <5 USD 9 USD Mostexpensive Efficiency/ Brightness 300USD/Year for 800 lumens 75 USD per year <10 USD per year Not yet efficient Environmentalfriendliness Low efficiency Contains mercury Most efficient, no toxic chemical Not yet efficient, no toxic chemical Costs of LEDs have Rapidly Dropped Source: Group presentation in MT5016 module and http://electronics.howstuffworks.com/led4.htm http://www.theverge.com/2013/10/3/4798602/walmart-gets-aggressive-on-led-bulb-pricing
    • 7. Incandescent Lights Electricity is generated by voltage across electrodes Poor efficiencies (most of the power is emitted as heat or non-visible electro-magnetic radiation) Also large size Big connector, bulbs, filaments Filament
    • 8. Fluorescent Lighting Electricity also generated by voltage across electrode Better efficiencies emits about 65% in 254nm line (visible) and 10–20% of its light in 185nm line (UV) UV light is absorbed by bulb's fluorescent coating (phosphors), which re-radiates the energy at longer “visible” wavelengths blend of phosphors controls the color of light But still large device Bulb, Connector, gases
    • 9. Outline Existing state of lighting Light emitting diodes (LEDs) Organic light emitting diodes (OLEDs) Laser Diodes Applications for Laser Diodes
    • 10. LEDs are basically a PN junction on a Semiconductor Substrate Voltage difference causes electrons and holes to recombine and thus release photons Amount of energy in photons (and thus wavelength of light) depends on band gap
    • 11. Typical LED Characteristics SemiconductorMaterial Wavelength Colour VF@ 20mA GaAs 850-940nm Infra-Red 1.2v GaAsP 630-660nm Red 1.8v GaAsP 605-620nm Amber 2.0v GaAsP:N 585-595nm Yellow 2.2v AlGaP 550-570nm Green 3.5v SiC 430-505nm Blue 3.6v GaInN 450nm White 4.0v Different Materials for LEDs Emit Different Wavelengths and thus Emit Different Colors
    • 12. But other changes in materials lead to improvements in efficiency One measure of efficiency is Photons per electrons: first LEDs in 1960s generated .0001 photons/electron But efficiency is a vague term because our eyes are more sensitive to some colors than others More popular measure of efficiency is lumens per Watt; function of internal efficiency: amount of lumens generated extraction efficiency: % of lumens that actually escapes Must create the right combination of materials (and processes) to achieve high luminosity per Watt Orton, J, 2009. Semiconductors and the Information Revolution: Magic Crystals that made IT Happen, NY: Academic Press
    • 13. Must find materials that Emit light in visible spectrum Have short radiativelifetime (high probability of radiativerecombination for electrons and holes) Minimize non-radiativerecombination with high crystal purity and structure Maximize the possibility of radiativerecombination by bringing together holes and electrons in a small space (such as double hetero-structure or quantum well) And also design the device such that most of the light is extracted, i.e., escapes Orton, J, 2009. Semiconductors and the Information Revolution: Magic Crystals that made IT Happen, NY: Academic Press
    • 14. Improvements in Luminosity per Watt have Occurred Source: Lima Azevedo, Granger Morgan, Fritz Morgan, The Transition to Solid-State Lighting, Proceedings of the IEEE 97(3) Luminosity per Watt
    • 15. New Processes Also Helped Because these materials do not naturally occur and because the processes impacted on the efficiency of an LED, scientists and engineers also created new processes for these new materials These processes include Liquid phase epitaxy MOVPE (metal organic vapor phase epitaxy) MBE (molecular beam epitaxy) Electron beam irradiation MBE allowed better control over the ratio of materials and the structures of the devices Orton, J, 2009. Semiconductors and the Information Revolution: Magic Crystals that made IT Happen, NY: Academic Press
    • 16. Most Recent Color is Blue Bottleneck for making white LEDs for many years was in blue lasers (need red, blue, and green lights) Efficient blue lasers did not exist until ShujiNakamura improved the efficiency of blue LEDs in late 1990s by using GaInN Blue LEDs enabled white LEDs and thus the use of LEDs for lighting Second, blue lasers enabled smaller memory storage areas in CDs because shorter wavelength than red lasers Finally, he developed a new growth technique called epitaxial lateral over growth, which enabled lower dislocation densities in blue lasers Orton, J, 2009. Semiconductors and the Information Revolution: Magic Crystals that made IT Happen, NY: Academic Press
    • 17. How to achieve White Color LED Mixture of Red, Green & Blue color to get white color LED. Involved electro-optical design to control blending & diffusion of different colors Involved coating of an blue LED with phosphor of different colors to produce white light. Fraction of blue light undergoes the Stokes Shift being transformed shorter wavelength to longer wavelength. RGB White LED Phosphor Based White LED LED Die Phosphor Phosphor Based White LED Spectrum of Phosphor LED RGB Color Chart
    • 18. Warm white Cool white Daylight white Phillips and Samsung have created LEDs that emit 200 lumens and they concluded that maximum theoretical efficiency is 400 lumens per Watt. http://www.greentechmedia.com/articles/read/philips-ups-led-ante-with-200lumens-per-watt-tube. http://www.ledinside.com/node/16905 Further Improvements in Efficiency Have Continued to Occur and More are Still Possible According to DoE, Phillips, and Samsung
    • 19. DoE’s Projected Increases in Efficiency of LEDs
    • 20. Fluorescent Source: Lima Azevedo, Granger Morgan, Fritz Morgan, The Transition to Solid-State Lighting, Proceedings of the IEEE 97(3), March 2009 More Detailed Projections for LEDs by DoE
    • 21. Source: Roland Haitz, Jeffrey Tsao, Solid-state Lighting: The case 10 years after and future prospects, Phys. Solidi A 208 (1): 17-29, 2011 Costs are also Falling (Dotted Line) due to Greater Efficiencies and Changes in Scale
    • 22. Through-hole LED Lead frame based Advantages Low cost & easy rework Higher mechanical shock resistant Better light extraction with optic designed viewing angle Disadvantage Size Printed Circuit Board based Advantages Size, thickness SMT process, more popular Disadvantage Less immunity to environmental No optic design, customized viewing angle Complicated process Surface Mount LED Both reductions (smaller LEDs) and increases in scale (bigger wafers/equipment) drive Cost Reductions
    • 23. *See fourth session on ICs and discussion of displays for more details on why costs fall as substrates and equipment are made larger. Wafers for ICs are now 12” and will soon be 18” Source of figure: http://www.electroiq.com/articles/sst/2012/02/led-manufacturing-highlights-from-strategies-in-light-day-2.html Wafer Sizes Have and Will Become Larger*
    • 24. LED CFL Incandescent Light bulb projected lifespan 50,000 hours 10,000 hours 1,200 hours Watts per bulb (equiv. 60 watts) 10 14 60 Cost per bulb $35.95 $3.95 $1.25 KWh of electricity used over50,000 hours 500 700 3000 Cost of electricity (@ 0.10per KWh) $50 $70 $300 Bulbs needed for 50k hours of use 1 5 42 Equivalent 50k hours bulb expense $35.95 $19.75 $52.50 Total cost for 50k hours $85.75 $89.75 $352.50 Relatively Recent Cost Comparison But most recent price <$10 (USD) for LEDs Sources: http://www.tomsguide.com/us/light-bulb-guide-2014,review-1986.html; http://www.tomsguide.com/us/light-bulb-guide-2014,review-1986.html $9 $9 $59
    • 25. Can’t we design and package LED lights any better than this?
    • 26. Two LED-based Decorative Lights Available in Singapore
    • 27. LEDs for Greenhouses? Greenhouses enable more locally grown food, and thus lower transportation costs Build greenhouses in cities, something like vertical farms? LEDs make more light available for greenhouses in northern climates and thus increase their productivity http://nextbigfuture.com/2014/06/greenhouses-will-get-more-energy.html#more
    • 28. Smart Lighting and (Heating)? Easer to control LEDs via Internet with for example, tablet or smartphone Can set timing, adjust colors and brightness Various hardware are needed but getting cheaper due to better electronic components may be economical in office or other commercial buildings How about using electronics to sense presence and location of humans? Lights automatically turn on and off as people move Take this one step further: lights only illuminate spots where people are standing or looking Lighting as a service Source: Technology Review, Nov 5, 2012. http://m.technologyreview.com/blog/guest/28396/
    • 29. Upgrades lightings at no upfront cost Provides maintenance Provide free energy audits, technical assistance and its new financing option Share Electricity Savings from using LEDs More than 120 years in lighting businessWhat is Lighting-as-a-Service?
    • 30. Smart Heating with Infra-Red LEDs Direct beams of infrared light at people using Clever optics Servo-motors Infrared light heats people and reduces need for heating entire room Large infrared lamps? Or small infrared LEDs? People tracked with image sensors or Wi-Fi Useful for large open rooms (e.g., lobbies, atrium, lecture halls) or rooms rarely used Can reduce heating costs by 90% Economist, in the moment of the heat, economist, September 6, 2014
    • 31. Market for LEDs is Changing from Industrial Applications to General Lighting as US bans sale of 40 and 60Watt Incandescent Bulbs Source: http://www.semiconductor-today.com/news_items/2012/AUG/LED_090812.html
    • 32. http://www.ledinside.com/node/17226; April 24, 2013
    • 33. Outline Existing state of lighting Light emitting diodes (LEDs) Organic light emitting diodes (OLEDs) Laser Diodes Applications for Laser Diodes Bioluminescence
    • 34. OLEDs have many Advantages Cheaper to process than semiconductor materials Lower temperatures required Can be roll printed onto a substrate (see later slides in this session) Can put multiple colors on the same substrate Can stare at them, unlike other forms of lighting Thinner and more flexible These advantages enable more aesthetically appealing designs, even more than LEDs But they currently have higher cost, lower efficiency and shorter lifetimes than do LEDs
    • 35. What about Organic LEDs (OLEDs) Improvements in OLEDs are Occurring Source: Sheatset al, 1996, Organic Electroluminescent Devices, Science 271 (5277): 884-888 and ChangheeLee’s presentation slides; PPV: poly (p-phenylenevinylene)
    • 36. More Recent Data Improvements also continue to be made. According to a 2009 paper in Nature, a novel structural design for a white OLED is described that exhibits efficiencies of 90 lumens per watt and shows a potential for efficiencies as high as 124 lumens per watt Panasonic announced a white OLED with 114 lumens per Watt in 2013 Philips claims that efficiencies of 150 lumens per Watt can and will likely be achieved in the near future. http://www.technologyreview.com/news/413485/ultra-efficient-organic-leds/ http://panasonic.co.jp/corp/news/official.data/data.dir/2013/05/en130524-6/en130524-6.html
    • 37. Improvements are Driven by Creating Materials….. Creating materials that better exploit the phenomenon of electroluminescence is the main reason for the improvements shown in the previous slide Nitrides Polymers Polyfluorene Also new processes?
    • 38. What are the limits? To what extent can efficiencies be improved? costs be reduced? thinness be achieved? Lifetimes be increased? Are these limits determined by materials or processes? Can roll printing dramatically reduce costs; can increasing scale of roll printing equipment lead to much lower costs?
    • 39. Where will be the first application for OLEDs Ones that require thinness, flexibility, and/or multiple colors on a single substrate? Household lighting? Retail lighting? Clothing? Displays? How many improvements are needed before these applications become economically feasible?
    • 40. Household Lighting
    • 41. Retail Lighting Display New forms of eye catching layouts New types of Signs
    • 42. Clothing Flexible light panels sewn on clothing can provide brighter luminance compared to conventional safety clothing
    • 43. Outline Existing state of lighting Light emitting diodes (LEDs) Organic light emitting diodes (OLEDs) Laser Diodes they are similar to LEDs They are basically an LED with a cavity and a mirror to enable “optical amplificationbased on stimulated emissionofphotons” Applications for Laser Diodes Bioluminescence
    • 44. Semiconductor Lasers also benefit from the two mechanisms mentioned earlier Creating materials (and their associated processes) that better exploit physical phenomenon Creating combinations of materials that better exploit phenomenon of optical amplificationbased on stimulated emissionofphotons Helped by new processes that enable higher purity, better crystal structure, and better control over composition of materials Also better materials for heat sinks, solder, and mirrors Geometrical scaling Increases in scale: larger wafers/production equipment Reductions in scale: smaller sizes generally lead to lower threshold current densities (helped by new technologies)
    • 45. Different materials emit light at different wavelengths Laser types shown above the wavelength bar emit light with a specific wavelength while ones below the bar emit in a wavelength range. Non- semiconductor lasers (many kinds of lasers) are also shown in this figure
    • 46. Many Improvements to Lasers Reductions in threshold current, i.e., minimum current needed for lasing Reductions in Pulse Width of Lasers for faster switching Increases in Power of Lasers Improvements in cost and power for one type of laser (GaAs)
    • 47. Source: Materials Today 14(9) September 2011, Pages 388–397 Reductions in Threshold Current, i.e., Minimum Current Needed for Lasing to Occur, enable lower power consumption
    • 48. Reductions in Threshold Current Driven By: New structures Double hetero-structure Quantum wells Quantum dots Reductions in scale These new structures involve smaller dimensions Reductions in scale for a specific structure (along with other changes) also led to reductions in threshold current density Reductions in scale also lead to lower costs in the long run
    • 49. Double HeterostructureQuantum Well (edge emitter) (edge emitter) Vertical Cavity Surface Emitting Laser (VCSEL) (emits from the top and emits perpendicular to the top surface), cheaper to fabricate than others
    • 50. Source: NTT develops current-injection photonic-crystal laser http://www.physorg.com/news/2012-02-ntt-current-injection-photonic-crystal-laser.html DFB: Diffraction Feedback Laser VCSEL: Vertical Cavity Surface Emitting Laser Lower operating currents also for VCSEL
    • 51. Reductions in Threshold Current (2) Creating new combinations of materials; enabled both new emission wavelengths and better lasing at a single wavelength (purity and crystal strength are important: see next slide) New processes supported the reductions in scale and the creation of better materials Liquid phase epitaxy Vapor phase epitaxy Molecular beam epitaxy Metal organic vapor phase epitaxy Low pressure chemical vapor deposition
    • 52. Reductions in Pulse Width of Lasers http://www.nature.com/ nature/ journal/v424/n6950/fig_tab/nature 01938_F2.html
    • 53. Improvements in Power of Other Lasers for Defense, Medical (without affecting eyes) Yb: Ytterbium Tm: Thallium Er:Yb: Ytterbium- sensitized erbium http://spie.org/x26003.xml
    • 54. Source: Ultrafast fiber lasers, MartingFermannand Ingmar Hart, Nature Photonics, 20 Octobers 2013, 868-874 Using Multiple Fibers can Enable Even Higher Power Output
    • 55. Many Improvements to Lasers Reductions in threshold current, i.e., minimum current needed for lasing Reductions in Pulse Width of Lasers Increases in Power of Lasers Improvements in cost and power for one type of laser (GaAs)
    • 56. For a specific type of laser, e.g., GaAslaser diode Improvements are largely driven by creation of new materials and processes for making those materials Heat sink: heat must be removed in order to prevent overheating of laser Mirror: contaminants in mirror cause light to be focused on a spot and thus burn up the mirror Processes Fewer defects can have large impact on maximum power because small reduction in defects can lead to much higher power Faster processes leads to lower costs come from faster processing Also increases in scale of wafers and associated production equipment Source: Martinson R 2007. Industrial markets beckon for high-power diode lasers, Optics, October: 26-27. and conversations with Dr. Aaron Danner, NUS
    • 57. Improvements in Average Selling Price (ASP) and Power of Semiconductor Lasers Source: Martinson R 2007. Industrial markets beckon for high-power diode lasers, Optics, October: 26-27.
    • 58. Outline Existing state of lighting Light emitting diodes (LEDs) Organic light emitting diodes (OLEDs) Laser Diodes Applications for Laser Diodes Bioluminescence
    • 59. Applications for Lasers Telecom is a big one: covered in Session 10 But many others Information storage (e.g., CDs and DVDs) Processing of metals and other materials Printing, Surgery High power lasers for military, fusion Agriculture Automated vehicles Virtual reality games Some of these applications use laser diodes while other applications use other forms of lasers (gas and solid state lasers)
    • 60. Agriculture Laser leveled fields facilitate irrigation Better control of water GPS equipped tractors facilitate harvesting and seeding Remember prescriptive planting in session 4? Helps farmers plant seeds with greater precision using GPS and special seed drills
    • 61. Cost of Autonomous Vehicles (Google Car) Falls as Improvements in Lasers and Other “Components” Occur Source: Wired Magazine, http://www.wired.com/magazine/2012/01/ff_autonomouscars/3/
    • 62. Better Lasers, Camera chips, MEMS, ICs, GPS Making these Vehicles Economically Feasible 1 Radar: triggers alert when something is in blind spot 2 Lane-keeping: Cameras recognize lane markings by spotting contrast between road surface and boundary lines 3 LIDAR: Light Detection and Rangingsystem depends on 64 lasers, spinning atupwards of 900 rpm, to generate a 360- degree view 4 Infrared Camera: camera detects objects 5 Stereo Vision: two cameras build a real-time 3-D image of the road ahead 6 GPS/Inertial Measurement: tells us location on map 7 Wheel Encoder: wheel-mounted sensors measure wheel velocity ICs interpret and act on this data
    • 63. What an Autonomous Vehicle Sees
    • 64. Underwater Automated Vehicles For better oil exploration and fisheries For fish farms More than 50% of consumed fish are from fish farming But feeding the fish is costly and the waste damages the local environment Self propelled submersible fish pens can move fish to food and disperse waste Many sensors help make this more economically feasible
    • 65. Virtual Reality is becoming economically feasible partly because lasers are getting better and cheaper. Lasers sense the head movements so that the field of view changes.
    • 66. Outline Existing state of lighting Light emitting diodes (LEDs) Organic light emitting diodes (OLEDs) Laser Diodes Applications for Laser Diodes Bioluminescence
    • 67. Biological Materials Emit Light! How it Works 71
    • 68. Applications Lighting Can we use trees to provide street lighting? Or to provide indoor lighting? In-vivo imaging Anoninvasiveinsightintolivingorganisms Understanddiseaserelatedchangesinthebody Food industry Can help detect pathogens
    • 69. Challenges Very expensive to extract luciferase from fire flies Can we make better sources of bioluminescence through sequencing DNA, adjusting DNA, synthesizing DNA? Discussed in next session Can we put DNA into another living organism like has been done with spider silk? Or will the cost of luciferase as we scale up production? Just as cost of chemicals dropped as scale was increased
    • 70. Conclusions and Relevant Questions for Your Group Projects (1) The luminosity per Watt and their costs continue to be improved for LEDs and OLEDs because Scientists and engineers create new materials that better exploit the relevant phenomenon Also benefits from changes in scale How many further improvements are likely to occur? When will their costs become low enough or performance high enough to be economical for specific applications? Can we identify those applications, order in which they will become economical, and specific needs of each application? What does this tell us about the future?
    • 71. Conclusions and Relevant Questions for Your Group Projects (2) Improvements in lasers continue to occur Lower threshold current density Higher power Shorter pulse widths How many further improvements are likely to occur? When will their costs become low enough or performance high enough to be economical for specific applications? Can we identify those applications, order in which they will become economical, and specific needs of each application? What does this tell us about the future?