ieee web hosting - quantum dots, the future of led display...
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Jian Chen, Nanosys, Inc., Palo Alto, CA
IEEE Santa Clara Valley Consumer Electronics Society, 10/23/2012
Quantum Dots, The Future of LED Display Technology
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Back Lights for Flat Panel DisplaysCCFL to LEDs
CCFL LEDs
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Backlights with RGB LEDs
• RGGB used due to lower efficiency of green LEDs
• Real-time feedback needed to keep the correct white point due to color drifts mostly in green and red LEDs
2 Steve DenBaars, DOE SSL Market Introduction Workshop 2008
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White LED
White LEDs – sRGB ~ 70% NTSC
• White LEDs with high efficiency blue LED chips combined with yellow phosphor have become industry standard
• Compromise on color: sRGB~70% NTSC
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OLED Displays with Wide Color Gamut
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New Generation Phosphor: Quantum Dots
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What is a Quantum Dot?
• An inorganic highly efficient phosphor crystal grown through standard wet chemical manufacturing processes.
• Governed by their size, QDs have the unique capability to precisely generate a specific wavelength of light.
• They produce pure saturated colors or can be blended to a precisely defined white point
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Synthesis of Quantum Dots
T
Nucleation Growth
• QD synthesis done in solution chemistry typically using metal organic precursors in inert ambient
• Synthesis temp.: 100C-300C• Time: few seconds to hours• Size control
• Precursor material, concentration• Temperature• Time• Ligand• …
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Quantum Confinement in Quantum Dots
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e-
Small Quantum Dot
e-
Big Quantum Dot
d
∆E ≈π 2
h2
2meff d2
D
∆E ≈π 2
h2
2meff D2
φ = sin(π x / d)
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Spectral Characteristics of Quantum Dots
• Narrow FWHM: 30-40nm• Core/shell quantum dots
• High QY: ~90%• Long-term stability
• Continuous absorption spectra:
common excitation wavelength for green & red QDs
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• QDs embedded in organic polymer• Continuous roll-printed sheet• Replaces bottom diffuser• Exceptional color gamut• High uniformity
Quantum Dot Enhancement Film – QDEF
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Liquid crystal module
Top diffuser
Horizontal BEF
Vertical BEF
Light Guide Plate
Reflector
Backlight Unit with White LEDs
Bottom diffuser
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Liquid crystal module
Top diffuser
Horizontal BEF
Vertical BEF
QDEF
Light Guide Plate
Reflector
Backlight Unit with QDEF
• Blue LED replaces white LED
• QDEF replaces bottom diffuser
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Blue LED + QDEFWhite LED
Backlight with QDEF
• QDEF wavelengths can be precisely controlled: ±2nm
from Nanosys manufacturing process
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100% Adobe-RGB Solution with QDEF
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• QDEF wavelengths can be tuned continuously to target
different primary color coordinates and match color filters for optimal performance
Custom Wavelengths for Target Applications
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• White point can be easily tuned using different
loading of green and red QDs
6,500K
11,000K
Custom White Points for Target Applications
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• QDEF proven stable under highly accelerated testing• Equivalent operation lifetime in displays > 30,000hrs
Long-Term Stability of QDEF
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Roll-to-Roll Process for QDEF
• Roll-to-roll process for QDEF developed
• Good uniformity
achieved for white-point and brightness
uniformity requirements
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Core shell quantum dot phosphors
Optical film enhanced with core shell quantum dots
Rare earth element based
phosphor (YAG)
Blue LED enhanced with
YAG
White LED Backlight QDEF Backlight
QDEF – Bring Amazing Color to LCD Displays
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Thank You!