Hilmi Volkan Demir - KTH

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White LEDs Two most common methods for WLEDs � RGB LEDs: using 3 different (red-green-blue) LEDs � Color conversion LEDs: using luminescent materials (luminophor) on LEDs typically phosphors: EL of LED and PL of luminophors collectively generate white light Hilmi Volkan Demir Thin-Film Flip Chip (TFFC)
Phosphors vs. Nanophosphors Broad emitters, difficult to control precisely Yellow phosphors, color rendering index (CRI) ~ 70 Cool white appearance due to high correlated color temperature (CCT)~4000 -8000 K Red-green phosphors, CRI / CCT can be improved, but this comes at the cost of reduced luminous efficacy of optical radiation. Problems: stability, granularity, source of rare earth elements Hilmi Volkan Demir Narrow emitters, possible to control precisely PL Intensity(a.u) I 1.0 0.8 0.6 0.4 0.2 0.0 500 550 600 650 wavelength(nm) Cyan Green Yellow Red Using combinations of semiconductor quantum dot nanophosphors, It is possible to achieve warm white light CCT300 lm/W. l /W Superior photometric performance. Problem: Quantum efficiency is being improved. Further improvements required. Our focus: high optical quality WLEDs using quantum dot nanophosphors with specific spectral content of emission
Page 1 and 2: Nanophotonics to Combat Climate Cha
Page 3 and 4: … a very unfortunate unfortunate,
Page 5 and 6: What factors determine earth’s cl
Page 7 and 8: Carbon dioxide IPCC Climate Change
Page 9 and 10: CO 2, temperature change, and sea l
Page 11 and 12: Problems in ecology • According t
Page 13 and 14: 1997 2009 How are we doing? Kyoto P
Page 15 and 16: Can nanotechnology help to combat c
Page 17 and 18: How can we combat climate change us
Page 19 and 20: How does solid state lighting (SSL)
Page 21 and 22: Motivation for white LEDs (WLEDs) i
Page 23: Potential market of LED‐based pro
Page 27 and 28: Important photometric properties Fi
Page 29 and 30: Luminous efficacy (LE Luminous (LE
Page 31 and 32: Correlated color olor temperature (
Page 33 and 34: Nanocrystal quantum dot emitters 52
Page 35 and 36: Working principle energy transfer P
Page 37 and 38: Experimental achievement • Succes
Page 39 and 40: High‐quality, warm white LEDs int
Page 41 and 42: Photometric modeling • Aim: What
Page 43 and 44: Photometric trade‐offs T. Erdem ,
Page 45 and 46: Multilayered heteronanocrystals 1 0
Page 47 and 48: WLEDs tuned with onion‐like heter
Page 49 and 50: Optical Power P (a.uu) Surface stat
Page 51 and 52: Förster‐type energy transfer (FR
Page 53 and 54: Hybrid WLEDs enhanced enhancedwith
Page 55 and 56: Time‐resolved kinetics at donor e
Page 57 and 58: Kinetics of energy transfer S. Niza
Page 59 and 60: Green gap: green/yellow range J. M.
Page 61 and 62: Phhoton Count C 1000 100 10 Time‐
Page 63 and 64: FRET LEDs Color converted LED FRET-
Page 65 and 66: White light generating rresonant es
Page 67 and 68: Architectural tuning of color chrom
Page 69 and 70: Precise tuning of color with FRET C
Page 71 and 72: Ph.D. - Piled Higher and Deeper 3/1
Page 73 and 74: Localized plasmons • Collective l
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Physical explanation of localized p
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Dependence of resonance wavelength
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Plasmon‐coupled nanocrystals •
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Metal Enhanced Fluorescence Pompa e
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Scanning electron microscope (SEM)
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Our absorbance spectra of different
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Interactions between plasmons p and
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Spectral design of plasmon‐couple
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Photoluminnescence (couunts) 30000
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Material on quartz substrate Only S
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How can we combat climate change us
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Today - in 2010 • Nanocrystal bas
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Conclusions • Climate change is a
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Device and Sensors Group Demir lab
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Our research program • Biomimetic
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Hilmi Volkan Demir - KTH

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