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Frontiers of Engineering Reports on Leading-Edge Engineering from the 2009 Symposium (2010) / Chapter Skim
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Light-Emitting Diode Technology for Solid-State Lighting--Mike Krames
Pages 67-76

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From page 67...
... Since then, InGaN-based LEDs have become more efficient and even more powerful, and the availability of suitable phosphors has increased; today the vari ety, light output, and quality of LED-based white light has reached the point that it is beginning to unseat conventional lighting technologies in general illumination 
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From page 68...
... . When sufficient positive external voltage is applied across Ohmic contacts to the p- and n-type regions, the built-in electric field across the p-n junction is reduced, thereby initiating current flow.
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From page 69...
... In many cases, current spreading means are employed to provide uniform electrical injection within the thin epitaxial layers.
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From page 70...
... emission wavelength at reasonable operating current densities. Also shown is the human eye responsivity as determined by the photopic luminosity function, V(l)
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From page 71...
... WHITE LEDS Although the combination of separate blue, green, and red LEDs can be tuned to make white light, the most common approach applied in industry is to downconvert blue, violet, or UV light into longer wavelength light by using phosphors, which are excited by the LED primary emission. The phosphors are typically applied in various ways around or on top of the LED chip.
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From page 72...
... Incandescent Tungsten LED Hg 200 1,000 10,000 LED Wavelength (nanometers) FL Stokes' loss FIGURE 3 Equal-lumen spectra of white light emitters based on (i)
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From page 73...
... At right, typical luminous efficacies are indicated for conventional lighting technologies including incandescent tungsten, tungsten-halogen, compact fluorescent, tube fluorescent, and high-intensity discharge lamps.
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From page 74...
... In addition, the low-voltage drive and fast switching speed of LEDs means lighting for the future could look very different from the lighting we know today. It may include dynamic control features for automatic mood-setting or tuning of intensity and color to increase workforce productivity or simply to elevate people's moods.
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From page 75...
... 0.5In0.5P/GaP light-emitting diodes exhibiting >50% external quantum efficiency. Applied Physics Letters 75(16)
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Key Terms

  • white light
  • applied physics
  • physics letters
  • led chip
  • external quantum

  • blue light
  • maximum luminous
  • visible spectrum
  • light emitting
  • blue led

  • led package
  • led products
  • light output
  • light extraction
  • applied physic

  • vapor deposition
  • physic letters
  • photopic luminosity
  • yag phosphor
  • fluorescent lamp

  • crystal lattice
  • operating lifetime
  • quantum efficiencies
  • incandescent tungsten
  • lighting technologies

  • phosphor powder
  • gan substrates
  • conventional lighting
  • luminosity function
  • chemical vapor


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