Light Sources of the Future –                                       OLED and beyondJanos Veres, CTO, janos@polyphotonix.co...
AgendaLightHow to turn electricity into light ?The solid state lighting revolutionThe next wave: LED and OLEDNew materials...
PolyPhotonixInnovative SME based in the North East of England within PETEC (The UK National Centre forPrinted Electronics)...
LightLight is electromagnetic radiation: waves and particles at the same timeProduced by exciting a substance with a varie...
Energy and excitation levels: gasesSharp, discrete energy levels for individual atoms/moleculesElectrons transitioning bet...
Energy and excitation levels: solidsSolids: atoms interact, energy levels start splitting, discrete levels become “energy ...
Incandescence and blackbody radiationEmission of light from a hot                Radiation of a blackbodybody due to its t...
Sunlight           Solar radiation spectrum             Radiation of a blackbody
From incandescence to exciting gases and solidsIncandescence                                    Thermionic emissionEmissio...
Electroluminescence: LEDsFirst practical visible device 1962 red(Holonyak, GE)p and n type layers deliver holes andelectro...
White LEDs  Emission is centered around a single peak: bandgap  White is achieved either by phosphors or RGB devices combi...
OLED      Certain organic materials are semiconductors!      Photoluminescence+ electronic transport=electroluminescence  ...
Organic semiconductors     • Molecular solids. Intrinsic semiconductors     • Localisation is strong (especially in amorph...
Organics are disordered  Molecular orientation, surrounding of molecules influences them                                  ...
Evaporated OLEDMultilayer structures for dedicated tasksElectrode mathcing, emission colour, carrier confinement          ...
Excited states in organic LEDs                                                    p-                         p+           ...
Source: Universal Display OLED review
Source: Universal Display OLED review
Quantum dotsSemiconductor nanoparticles that exhibit quantum confinement (typically <10nm)Nanoparticle: inorganic material...
Quantum confinement   ZnO has small effective masses and quantum effects can be observed for particle sizes <8nm   TiO2 ha...
Surface functionalisation Surface states need to be terminated Particles need to be separated to stop interacting Inorgani...
QD fabrication                                                    Epitaxy, patterned growth   E-beam lithographyEtch pilla...
QD fabricationSelf-organized QDs through epitaxial growth strainsStranski-Krastanov growth mode (use MBE, MOCVD)Islands fo...
QD fabricationReactions engineered to precipitate quantum dots from solutions or a host material (e.g. polymer)Surface is ...
Quantum dots - propertiesHigh quantum yieldNarrower and more symmetric emission spectra100-1000 times more stable to photo...
Quantum dots for white LEDEvident, QD Vision, Nanoco
Quantum dot electroluminescent devicesThe next step in solid state devices!Direct injection of holes and electrons into th...
QD for biology & sensing                           Source: Justin Galloway, Johns Hopkins
Lighting todayLighting is a $90B industry and growingrapidly2/3 of all artificial light is generated byfluorescent area li...
Towards LED and OLED                 Today                                             Tomorrow                           ...
LED growth     Strong growth despite high prices and recession in 2008-2009     Source: Strategies Unlimited)
The Haitz Law      1) Luminous flux per package increases 30 times each decade      2) Cost per lumen decreases by a facto...
OLED is real: displays and lighting                                      Displays                       Lihgting          ...
Real energy efficiency depends on the luminaire!OLED has the opportunity to be the luminaire itself                       ...
LED and OLED development expectations –DOE roadmapsBoth are predicted to offer important solutions to energy efficiency in...
OLED lighting today           Source: DisplaySearch
OLED lighting today – commercial devices
OLED lighting today -demosSource: Philips, GE, Add-Vision, Osram
Long term visionInherently large area and low glare light sourcePotentially ½ the power consumption of fluorescentWarm, pl...
The Printed Electronics industry will eventually become   as big as the semiconductor industryIt involves the printing of ...
Printed, felxible light –organic or inorganic•   Highly efficient operation•   High quality white light (and/or better col...
The Importance of DesignRichard Kirk, Founder of PolyPhotonix has a recognised background creating markets in thefield of ...
It’s not just the Science…..                               Working with artists via the creation                          ...
Printed Electronics in Architecture              Alcatel Boardroom, Paris, France   Radisson Stanstead Wine Tower, UK
Heathrow Terminal 5British Airways, First Class Lounge10,500 circuits25 meters x 2.5 metersAll circuits individually addre...
Advertising Experience with every outdoor company in Europe and North America Delivery and installation Integrated solutio...
FashionThe HSBC Advert was shown in 180 countries   Gareth Pugh 2007
Printed Electronics in AutomotivePioneered the use of printed Electroluminescence in transport applications with:Jaguar, B...
The UK Printable Electronics CentrePETEC                                      2x 8,000 sq ft clean rooms.                 ...
PolyPhotonix technology development•   Synergies with technology base for other projects at PETEC•   Secured significant g...
What does the futurte hold ? Future conceptsWireless lighting – Tesla experimentsColour tuning in a single layerTransparen...
Strechable LED arraysSmall LED “chiplets” connected with a wave-shaped wire meshEmbedded in silicone plasticApplications: ...
Lighting with trees ?Implanting gold nanoparticles into the leaves of the Bacopa Caroliniana plants.Under UV excitation, A...
SummarySolid state lighting is undergoing a revolutionLED and OLED are both taking off fastInitially high prices require t...
OLeds and Beyond- Light Sources of the Future Seminar
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OLeds and Beyond- Light Sources of the Future Seminar

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Here is a copy of Professor Janos Veres, Chief Technical Office at Polyphotonix, seminar which was presented in our studio in London. From zinc oxide and non-toxic nanocrystals to the super material grapheme Prof. Veres looked at current and potential directions for lighting technology and examine the implications for the way we use and design with light in the future

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OLeds and Beyond- Light Sources of the Future Seminar

  1. 1. Light Sources of the Future – OLED and beyondJanos Veres, CTO, janos@polyphotonix.comwww.polyphotonix.com
  2. 2. AgendaLightHow to turn electricity into light ?The solid state lighting revolutionThe next wave: LED and OLEDNew materials on the horizonRadical conceptsWhere is the lighting industry moving ?
  3. 3. PolyPhotonixInnovative SME based in the North East of England within PETEC (The UK National Centre forPrinted Electronics).Established in early 2009Focus on the application end of OLED technology - disruptive, radical uses in:Architectural lighting, medical devices and automotive lighting/ambient interiors
  4. 4. LightLight is electromagnetic radiation: waves and particles at the same timeProduced by exciting a substance with a variety of means(heat, light, charged particles, chemical or biological)Excitation and subsequent emission corresponds to transfer of energy between discrete levelsin matter
  5. 5. Energy and excitation levels: gasesSharp, discrete energy levels for individual atoms/moleculesElectrons transitioning between levels produce distinct absorption/radiation colours Bromine Deuterium Helium Hydrogen Emission spectrum Krypton Mercury Neon Water vapour Absorption spectrum Xenon
  6. 6. Energy and excitation levels: solidsSolids: atoms interact, energy levels start splitting, discrete levels become “energy bands”Discreet lines are more difficult to observe
  7. 7. Incandescence and blackbody radiationEmission of light from a hot Radiation of a blackbodybody due to its temperatureThe “Planckian Locus” in a colour space The sensitivity of the eye
  8. 8. Sunlight Solar radiation spectrum Radiation of a blackbody
  9. 9. From incandescence to exciting gases and solidsIncandescence Thermionic emissionEmission of light from a hot Heat induced flow of chargebody due to its temperature from a surface. Cathodoluminescence Beam of electrons excites a luminescent phosphor (television)Charge:Fluorescent sourcesElectrons (thermionic) emitted ionise a gas.The relaxation of gas molecules emit UV light.UV is in turn used to excite a phosphor.
  10. 10. Electroluminescence: LEDsFirst practical visible device 1962 red(Holonyak, GE)p and n type layers deliver holes andelectrons to a recombination zoneEmission colour is determined bybandgap of active layer From Kazarinov and Pinto, IEEE J. Quantum El. 30, 49, 1994
  11. 11. White LEDs Emission is centered around a single peak: bandgap White is achieved either by phosphors or RGB devices combined High colour rendering is a challengeSee http://en.wikipedia.org/wiki/Light-emitting_diode
  12. 12. OLED Certain organic materials are semiconductors! Photoluminescence+ electronic transport=electroluminescence Light Emitting Diodes can be built that resemble LED Visible lightLow workfunctioncathode hυCa, Li, Al etc. + + + + + + + - - - LUMO + + + 3–6 V - -+ + + - + - - + + - HOMO High workfunction - - - - - - Anode Au, ITO, Pt etc.
  13. 13. Organic semiconductors • Molecular solids. Intrinsic semiconductors • Localisation is strong (especially in amorphous materials) • bias for n or p type character due to electron donating/withdrawing groups O O Polythienylene- R R Vinylene (PTV) R N N R O n O S N perylenes R polyfluorenes O N O R R Pentacene X N X S R Oligo, poly- PPVs O N O -thiophenes n Y R n PTAANTDI derivatives R e- e- LUMO LUMO LUMO: orbitals overlap ambipolar h+ p-type n-type h+ HOMO HOMO Adopted from J. Veres, MRS Spring 2006 HOMO: orbitals overlap
  14. 14. Organics are disordered Molecular orientation, surrounding of molecules influences them Extended state May be a molecule, chain segment or domain e-LUMO 1. molecular energies vary due to local orientation & polarisation effects n-type Low dipole moment, symmetry Reduce impuritiesHOMO 3. Orbital size and shape Transition probability 4. Charge in orbitals p = n exp(–2R/r – DE/kT) e- DEh 2. molecular relaxation introduces further energy difference Larger molecules (i.e. extended states) help Adopted from J. Veres, MRS Spring 2006
  15. 15. Evaporated OLEDMultilayer structures for dedicated tasksElectrode mathcing, emission colour, carrier confinement Low work function metal Cathode ETL (Electron Transport layer) Alq3 HBL (hole blocking layer) Host:Dopant Various dyes HTL 2 (Hole Transport Layer) HTL 1 Triarylamines HIL (Hole Injection Layer) Anode ITO Copper-Phthalocyanine / Glass PEDOT PANI
  16. 16. Excited states in organic LEDs p- p+ recombination ↑↑ 1 ( ↑↓ + ↓↑ ) 1 2 ( ↑↓ − ↓↑ ) singlet exciton triplet exciton 2 ↓↓ radiative non-radiative non-radiative decay decay decayExcited stated decay following spin statistics:singlet: triplet ratio is 1:3, allowing only 25% efficiency by luminescencePhosphorescence:Certain metal complexes allow radiative emission from triplet states
  17. 17. Source: Universal Display OLED review
  18. 18. Source: Universal Display OLED review
  19. 19. Quantum dotsSemiconductor nanoparticles that exhibit quantum confinement (typically <10nm)Nanoparticle: inorganic material (e.g. CdSe) with a diameter less than 1nmProperties are tuned by the size of crystalline dotsCan be functionalised Source: Evident Technologies & AIST Today Vol.6, No 6 (2006)
  20. 20. Quantum confinement ZnO has small effective masses and quantum effects can be observed for particle sizes <8nm TiO2 has large effective masses thus quantum effects are difficult to observe ZnO TiO2 4 ZnO TiO2 Eg (eV) 4 Eg (eV) 3 3 400 400 λonset (nm)λonset (nm) 350 350 300 300 250 250 0 5 10 0 5 10 d (nm) d (nm) Source: J. Galloway, Johns Hopkins univ. 2007
  21. 21. Surface functionalisation Surface states need to be terminated Particles need to be separated to stop interacting Inorganic shell grown Polymeric functionalisation- solubility, dispersibility! Specific binding sites: sensing/medical applicationsVoura, E. B., Jaiswal, J. K., Mattoussi, H. & Simon, S. M. Nature Med.2004(10), 993–998 Source: Evident Technologies
  22. 22. QD fabrication Epitaxy, patterned growth E-beam lithographyEtch pillars in quantum well heterostructures1D vertical confinement due to mismatch of Growth on patterned substratesbandgaps (potential energy well) Grow QDs in pyramid-shaped recessesPillars provide confinement in the other 2 Recesses formed by selective iondimensions etchingDisadvantages: Slow, low density, defects Disadvantage: density of QDs limited by mask patternA.Scherer and H.G. Craighead. T. Fukui et al.Appl. Phys. Lett., Nov 1986. Appl. Phys. Lett. May, 1991
  23. 23. QD fabricationSelf-organized QDs through epitaxial growth strainsStranski-Krastanov growth mode (use MBE, MOCVD)Islands formed on wetting layer due to lattice mismatch (size ~10s nm)Disadvantage: size and shape fluctuations, orderingControl island initiationInduce local strain, grow on dislocation, vary growth conditions, combine with patterning P. Petroff, A. Lorke, and A. Imamoglu. Physics Today, May 2001.
  24. 24. QD fabricationReactions engineered to precipitate quantum dots from solutions or a host material (e.g. polymer)Surface is capped so the dot remains chemically stableCan form “core-shell” structures, by sequential growthTypically group II-VI materials (e.g. CdS, CdSe)Disadvantage: Size variations ( “size dispersion”) C. B. Murray, et al Annual Rev. Mater. Sci. 30, 545, 2000.
  25. 25. Quantum dots - propertiesHigh quantum yieldNarrower and more symmetric emission spectra100-1000 times more stable to photobleaching than organicsHigh resistance to photo-/chemical degradationTunable wave length range 400-4000 nm CdTe J. Am. Chem. Soc. 2001, 123, 183-184
  26. 26. Quantum dots for white LEDEvident, QD Vision, Nanoco
  27. 27. Quantum dot electroluminescent devicesThe next step in solid state devices!Direct injection of holes and electrons into the quantum dotsChallenges: surface states on dotsBalancing carrier transport and isolation of quantum dots for their optical propertiesPotentially coatable, printable like OLED ! J.M. Caruge et al, Nature Photonics, 2, 247, 2008
  28. 28. QD for biology & sensing Source: Justin Galloway, Johns Hopkins
  29. 29. Lighting todayLighting is a $90B industry and growingrapidly2/3 of all artificial light is generated byfluorescent area lightsQuality of light, glare, efficacy, and toxicmercury are fluorescent’s shortcomings
  30. 30. Towards LED and OLED Today Tomorrow ? inefficient environmental impact LED: efficient spot light OLED: efficient area light LED and OLED will dominate 31
  31. 31. LED growth Strong growth despite high prices and recession in 2008-2009 Source: Strategies Unlimited)
  32. 32. The Haitz Law 1) Luminous flux per package increases 30 times each decade 2) Cost per lumen decreases by a factor of 10 each decade. Source: Roland Haitz, Hewlett-Packard Labs, 1998
  33. 33. OLED is real: displays and lighting Displays Lihgting 34
  34. 34. Real energy efficiency depends on the luminaire!OLED has the opportunity to be the luminaire itself LED Incandescent CFL Picture or graphic here Source: DOE Round 9 CALiPER Report
  35. 35. LED and OLED development expectations –DOE roadmapsBoth are predicted to offer important solutions to energy efficiency in the next 10 yearsBoth can achieve similar power efficiencies.OLED is approximately 3 years behind LED Source: DOE Roadmaps
  36. 36. OLED lighting today Source: DisplaySearch
  37. 37. OLED lighting today – commercial devices
  38. 38. OLED lighting today -demosSource: Philips, GE, Add-Vision, Osram
  39. 39. Long term visionInherently large area and low glare light sourcePotentially ½ the power consumption of fluorescentWarm, pleasing colorGreen technology – no mercuryInnovative form factors in the future Source: Osram, Konica Minolta, Acuity Brands 40
  40. 40. The Printed Electronics industry will eventually become as big as the semiconductor industryIt involves the printing of materials to create electronics.• It can be very large areas Outdoor Billboards• It can offer new forms Flexible, Rollable and invisible• It can be cheaper Low cost materials and manufacturing compared to conventional electronics• It can offer improved performance over conventional electronicsIt creates new possibilities for business, new businesss and wealth creation. The step Printed Electronics from integrated circuits is as equally important as that from vacuum tubes to transistors
  41. 41. Printed, felxible light –organic or inorganic• Highly efficient operation• High quality white light (and/or better colours)• Long lifetimes• Thin, flat, large area ‘lambertian’ light source – architects love the idea• Low voltage, DC driven• ‘Printable’ – sheet or ‘roll to roll’• Resistant to shock and vibration• Multitude of applications• Conformable and flexible, ability to integrate into architecture OLED automotive applications
  42. 42. The Importance of DesignRichard Kirk, Founder of PolyPhotonix has a recognised background creating markets in thefield of Printed Electronics Jonas 2006 Animated Wallpaper
  43. 43. It’s not just the Science….. Working with artists via the creation of an art foundation
  44. 44. Printed Electronics in Architecture Alcatel Boardroom, Paris, France Radisson Stanstead Wine Tower, UK
  45. 45. Heathrow Terminal 5British Airways, First Class Lounge10,500 circuits25 meters x 2.5 metersAll circuits individually addressableCreated by artists that Elumin8 sponsored in the pastManufacture, design and install, 1/10th of the cost of an equivalent LED wall Troika, London
  46. 46. Advertising Experience with every outdoor company in Europe and North America Delivery and installation Integrated solutions Examples of outdoor installations in Paris.
  47. 47. FashionThe HSBC Advert was shown in 180 countries Gareth Pugh 2007
  48. 48. Printed Electronics in AutomotivePioneered the use of printed Electroluminescence in transport applications with:Jaguar, Bentley, Rolls Royce, BAE, Lotus, Aston Martin, Ford, Ascari, JCB,MOD, Nascar, Toyota, Westland, Nissan among others. Jaguar CXF
  49. 49. The UK Printable Electronics CentrePETEC 2x 8,000 sq ft clean rooms. Pilot line processes developed for •Organic Thin Film Transistors (OTFT); •Organic Photovoltaics (OPV); •Solid State Lighting (SSL) state of the art equipment set and world class industry expertise
  50. 50. PolyPhotonix technology development• Synergies with technology base for other projects at PETEC• Secured significant grants for funded projects, over £2 M• Working with technology providers to source, license existing materials/processes• Building a development process line• Exploring proprietary process technologies for follow up phase• PolyPhotonix is aiming to be one of the first to market with an OLED product.
  51. 51. What does the futurte hold ? Future conceptsWireless lighting – Tesla experimentsColour tuning in a single layerTransparent devicesPhotovoltaics and lighting combinedLighting elements integral part of building elements
  52. 52. Strechable LED arraysSmall LED “chiplets” connected with a wave-shaped wire meshEmbedded in silicone plasticApplications: surgical gloves, strechable displaysSource: Kim et al, Nature materials, 9, 929, 2010
  53. 53. Lighting with trees ?Implanting gold nanoparticles into the leaves of the Bacopa Caroliniana plants.Under UV excitation, Au nanoparticles produce a blue-violet fluorescence to trigger ared emission in the surrounding chlorophyll.Source: Prof Shi-Hiu Chang, Taiwan
  54. 54. SummarySolid state lighting is undergoing a revolutionLED and OLED are both taking off fastInitially high prices require targeting unique applicationsThere is plenty of opportunity to innovate:LED/OLED developments with quantum dots will be significant!

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