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Mo m present_monday_light interacting materials


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Monday Presentation MoM Summer School 2017- Light interacting materials: photoluminescent materials, dichroich glass, acrylic fluoorescent sheets as solar concentrators, new generation of PV cells harvesting in diffused light

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Mo m present_monday_light interacting materials

  1. 1. Light Interacting Materials Light Interacting Materials All MoM materials, this document included, belong to MoM-Matters of Matter authors and are distributed under Creative Commons Attribution-NonCommercial- ShareAlike 4.0 International License as OER Open Educational Resources . This project has received funding from the European Union's Erasmus + Programme for Education under KA2 grant 2014-1-IT02-KA201-003604. The European Commission support for the production of these didactical materials does not constitute an endorsement of the contents which reflects the views only of the authors, and the Commission cannot be held responsible for any use which may be made of the information contained therein. Funded by EU under the Erasmus+ KA2 grant N° 2014-1-IT02-KA201-003604_1.
  2. 2. Light Interacting Materials Phosphorescence
  3. 3. Light Interacting Materials Writing with light on photoluminescent materials • Do all colours activate photoluminescence ? • Does it depend on their intensity? • How’s the emitted light color compared to the excitation light? Light should be of the right frequency • No matter the intensity /power • Higher f than the emitted one • The material should be able to absorb f  Quanta of light the energy appears to be concentrated in discrete packets called photons. Photoluminescence can’t be explained by light wave theory YOU NEED • LED Torch, UV Torch • Colored filters (blue, red, …) • Photoluminescent paper • Red lamp 100 W
  4. 4. Light Interacting Materials Photoluminescence …how does it work? 1. All electron transitions from the excited to the ground state are non-radiative except for the last one. 2. Energy conservation part of E is lost as heat due to vibrations --> the emitted light is of lower frequency/longer wavelenght = less energetic 3. If the vibration is less intense (i.e. liquid nitrogen) -> change in the emitted colour (higher f) may be observed.* 4. Excitation energy may be also chemical (chemiluminescence) , or mechanical (triboluminescence) 1 2 4 3 See video how florescence works slide 9
  5. 5. Light Interacting Materials Studying emissions of photoluminescent samples WHEN SHOULD YOU TURN ON THE UV LEDS ? EVERY 0,02 SEC FOR 0,001 SEC Rare Earths/Inorganic Aluminates: «poor, dim» eco light from atoms (visible in almost total darkness) • not radioactive, • lasting 8 hours: after 1 hour 90% of light decay then stable for 7 hours approx. • little % of heavy metals, 20 times less than USA regulations • everlasting, recyclable,
  6. 6. Light Interacting Materials http:// Alienskin L.E.S.S RURAL ECO STREET LIGHTS Photoluminescence for energy saving Applications
  7. 7. Light Interacting Materials Fluorescence - When light excitation ceases light emission stops almost immediately (10^-8 sec)… … while in Phosphorescence light is still emitted long after excitation is over Phosphorescence VS FluorescencePhosphorescence VS Fluorescence By Jacobkhed - Own work, CC BY-SA 3.0, Common processes of electron interaction with light. Absorbed radiation may be emitted by vibrational relaxation, fluorescence, or phosphorescence
  8. 8. Light Interacting Materials Fluorescence Turn on your Black Light! = UV light
  9. 9. Light Interacting Materials Detergents, toothpaste Anti counterfeiting Bleached paper Hot glue Minerals Tonic water Testing water for Petroleum Jelly – Vaseline contamination Body fluids blood, urine semen Bocteria, moulds
  10. 10. Light Interacting Materials Acrylic fluorescent sheets/rods
  11. 11. Light Interacting Materials Can you imagine PV solar concentrators? Drawbacks • Sun Tracking mechanical movement • Large reflecting area • Rather large PV cell area • Superheating in focus -> efficiency loss • Difficult (and dangerous!) to integrate in buildings OPTICAL CONCENTRATORS: MIRRORS + LENSES Source public domain
  12. 12. Light Interacting Materials Acrylic fluorescent PV concentrators • Optical effect or real concentrators? • Acrylic rods VS fiberoptics • Refraction plus fluorescence • Harvesting best in diffused light
  13. 13. Light Interacting Materials 1 The Physics behind it: light guide + fluorescence Reflected Light guide: concentrated at the edges Transmitted & Escaped The incident radiation is «compressed» in the wavelengths that optimize the PV cell efficiency  Used in stacks to exploit different kinds of solar cells Source: By Levita.lev (Own work) [CC BY-SA 3.0 ( or GFDL (], via Wikimedia Commons Multiple total internal reflections
  14. 14. Light Interacting Materials 1 Red 1m Yellow 0,5m Green 0,25m Can you explain what’s happening?
  15. 15. Light Interacting Materials 1 FACTS If you shine light from one of the extremities • Incident light is white, the acylic rod is yellow green fluo • The longer the rod, the more the emitted light turns to reddish Possible (consinstant) explanation • The longer the rod and the greater the possibility that the green component light will be absorbed by the fluorescent pigments which riemit in red (possible more pigments absorbing UV riemitting green and absorbing green riemitting Red) • Is it the same with blue and UV light? spectrophotometer • Test PV cells with different rod lengths Is there an optimal length for best efficiency? • Is the effect the same even if you shine from the side surface?
  16. 16. Light Interacting Materials Acrylic fluorescent sheets for -indoor photovoltaics -smart windows -harvesting in diffuse light (Northern countries)
  17. 17. Light Interacting Materials 1 Seen at International Makers Faire Rome October 2015 Inspiration …
  18. 18. Light Interacting Materials 1 • Eni photovoltaic shelter can reach a 500 Watt [nominal] production of Electrical Energy • 192 yellow clear sheets . • Pigments have been specifically patented by ENI • ENI Photovoltaic Shelter Eindhoven University of Technology A2 Den Bosch The Netherlands Free download @ nellis_M.pdf
  19. 19. Light Interacting Materials Engineering challenges • What’s the gain of having solar cells at the edges? What’s the efficiency? • How much surface is needed to harvest enough light? Edges loss? • Best acrylic sheet colour? • Best incident light colour? Best incidence angle? Ratio of Edges surface/Harvesting area VS PV cell efficiency or output for a fixed luminance. Direct or diffused light? 1 1/2 1/8 1/4 N.B BEST example of PBL and IBSE open inquiry Alligned with cutting edge research makers faire 3^,4^ Maturità 5^
  20. 20. Light Interacting MaterialsThe acrylic fluo PV solar concentration lamp Rome Makers Faire European edition 2016!
  21. 21. Light Interacting Materials PV cells
  22. 22. Light Interacting Materials 1 1^ generazione : silicio monocstallino Alta efficienza>25% Sole pieno 2^ generazione : film sottile silicio amorfo Alta resistenza (Flessibilità ) Anche luce diffusa ea bassa intennsità 3^ generazione: organico e ibrido Polimeriche o organiche flessibili Bassi costi di produzione Possibilità di fine tuning delle proprietà molecolari
  23. 23. Light Interacting Materials Investigate the best option for • Building facades • Curved surfaces • Roofs with possible shadow casting elements • Indoor applications • Portable applications • IoT, wearables and pervasive sensors network Test • Illuminance lux (luminous flux per unit area) • Light intensity, direct/diffuse light, incidence angle dependance • Light source, incident wavelenghts, UV, IR • Efficiency PV cells: 3° generation and beyond …
  24. 24. Light Interacting Materials 1Angle Wavelength
  25. 25. Light Interacting Materials Dichroic film/glass
  26. 26. Light Interacting Materials Can you guess the missing colour? ?
  27. 27. Light Interacting Materials Reflected and transmitted frequencies are complementary ones If the background is not black some of the transmitted light is reflected back, hence the colour of the glass (third color)
  28. 28. Light Interacting Materials 1 The two most common types of filters in use today are absorption filters that absorb unwanted wavelengths and interference filters that remove selected wavelengths by internal destructive interference and reflection. Colour filters secondary absorption  Hot filters more accurate & efficient  Cool filters Magenta traditional filter: absorbs green light Magenta interference filter: reflects green light REFLECTION
  29. 29. Light Interacting Materials Can you explain what’s happening? YOU NEED • Black and white paper • Dichroich glasses YOU NEED • Add a mirror The mirror reflects back all light. Transmitted light combines with reflected one and makes white!looks transparent
  30. 30. Light Interacting Materials 1 • The colors shown are in reflection since there is no loss (no absorption), • the colors in transmission will be complementary. • Top row shows subtractive primary colors (yellow- cyan- magenta) but those in transmission will be additive (red green and blue) • vice versa for the lower three
  31. 31. Light Interacting Materials Can you explain what’s happening? Black & white paper + mirror The photographer is shadingn the bottom right corner Only black & white paper. The photographer is shading the disk bottom
  32. 32. Light Interacting Materials «Chamaleon film» Transmitted/reflected colours depend on both viewing angle & light incidence angle Angle Transmitted  … … …
  33. 33. Light Interacting Materials 1 References
  34. 34. Light Interacting Materials Same effect with dichroich film, a cheaper aletrnative to dichroic glass composed of hundreds of layers of polymer films with different refractive indexes.
  35. 35. Light Interacting Materials 1 “Place the radiant light film on a white sheet of paper - tilt it at different angles and observe the different colors. Now place against black background and tilt – is there a difference in its appearance? Fold a piece over, creating two layers. If you sandwich the layers flat against each other and repeat the experiments does anything change? Now hold the folded over piece so that there is some space between the layers (put a finger or two between the layers) and shine light in the middle. Can you produce green or other colors you couldn’t produce when the material was just one layer?» Source: More puzzling questions …
  36. 36. Light Interacting Materials 1 The Physics behind it: thin-film interference Dichroic filters are manufactured using multi- layered thin film coatings that are deposited on glass using vacuum deposition. They work on Interference principle Through the number and thickness of the films and the angle of the incident light, control over the color of light produced is possible coating glass * * *phase change 180° - half wavelength ejs_bu_ThinFilm –Java - off line
  37. 37. Light Interacting Materials 1 Thick films VS thin films A. Why thick films DO NOT exhibit visible interference? R. ATTENUATION (= amplitude decreases)  colours are too faint to be observable
  38. 38. Light Interacting Materials Thin films: APPLICATIONs • Laser mirrors • [Superhydrophobic surfaces] • Low Emissivity coatings (E-coatings) reduce heat loss in winter decrease heat gain in summer • … Thursday: «Climate change & the 2 °C challenge»
  39. 39. Light Interacting Materials Creativity and innovation
  40. 40. Light Interacting MaterialsMoM-Light for design… «Change your light» VIDEO Smart lamps with new materials
  41. 41. Light Interacting MaterialsMoM-Light for design…
  42. 42. Light Interacting Materials MoM-Light for design…
  43. 43. Light Interacting Materials Polarization
  44. 44. Light Interacting Materials Polarized ballet Plastic (no stress no birifrangence) + Sellotape Superimposed layers • How many? • At what angles? Put it between PC screen (open a white page) and polarization filter NOW ROTATE the polarization filter! AWESOME!
  45. 45. Light Interacting Materials Polarized lamps: 360° of colours This lamp exploits the light emitted by a bulb and polarised by two polariser filters. Between the two filters you can put superimposed layers of plastic, cellophane or tape to create optical effects with a lot of different colour shades changing as the filters rotate.
  46. 46. Light Interacting Materials 1 A Systematic study