Quantum Dots. for High Color Gamut LCD Displays Using an On-Chip LED Solution

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1 Quantum Dots for High Color Gamut LCD Displays Using an On-Chip LED Solution By Juanita Kurtin, Norbert Puetz, Brian Theobald, Nathan Stott, and Julian Osinski Pacific Light Technologies Portland, OR SID Display Week, Paper 12-5, June 3,

2 About PLT HQ in Portland, OR Founded May, 2011 Founders and original IP from SpectraWatt 35 employees/consultants On-chip quantum dots the preferred solution

3 Bandgap (ev) QD Downconverters The Next Big Thing Blue LED pump Downconverted emission Bulk Semiconductor (Infra Red) QD Size (nm) Highly uniform semiconductor epitaxy in a flask Nanoparticles absorb in the blue, re-emit elsewhere in the visible Precise peak emission placement (± 2 nm) Very narrow emission spectra (<35 nm FWHM) Very high efficiencies 3

4 QD Nanoparticle Synthesis not all are created equal Conventional Quantum Dots PLT Quantum Dots 1 Emission Absorbance 0.5 No Overlap Wavelength (nm) Optical properties controlled by size, materials, shape Property of no-self-absorption reduces loss

5 QDs Provide Improved Efficiency and Color Gamut Standard LED sources for BLUs waste energy. Gamut is determined by filters. PLT QD sources for BLUs provide a customized match to color filters. Gamut is determined by QD peaks. 1.2 Legacy Ce:YAG LED source PLT BLU - 539nm + 635nm QDs Filter functions Wavelength (nm) Higher system throughput can provide 20% electrical efficiency benefit for reduced power consumption 5

6 REC 2020 Coverage Wide Color Gamuts Require Narrow Spectral Widths play to quantum dots strengths Rec example 1.0 Red Green Blue 30nm 60nm nm 30nm 60nm Wavelength (nm) 110% 100% 90% 80% 70% 60% 50% 40% Spectral Width (nm) Gamut coverage drops off substantially as spectral width of primaries increases 6

7 Three methods of QD integration On-chip: Drop-in replacement, QDs in the LED package Minimum material quantity requirements Maximum temp and flux performance demand No BLU re-design required QDs QDs On-edge: Sealed optic between LEDs and edge-lit BLU Intermediate material and performance demands Source: QD Vision On-surface: Film covers entire screen area Maximum material quantity required Minimum temp and flux performance demand QDs Source: Nanosys 7

8 Previous QD challenges precluded on-chip operation Compatibility with LED silicones Sensitivity to moisture: hermetic seals required Sensitivity to high optical intensities and temperatures: significant quenching - 150C curing temperature - 260C solder reflow - Non-hermetic use condition at elevated temperatures and optical flux New QD designs at PLT have mitigated these shortcomings 8

9 On-chip LED Packages for Display Backlights Typically made by dispersion / volume casting Red + green QDs mixed into silicone Dispensed and cured in package as usual Works with any low to mid-power package size Operating flux W/cm 2, T = C This package type also often used for SSL applications 5630 package with QDs in silicone Dispersion cast PLT QD LED On-chip Quantum Dots 7020 package 9

10 PLT Results of Intensity Dependence Other QDs Conditions: room temp, 3mm laser spot at 450 nm on a red QD + silicone film, pulsed For PLT materials, no cliff observed up to 50 W/cm, measured in silicone at ambient conditions Other tests have been made out to 1000 W/cm2

11 Temperature Dependence: Low thermal quenching New PLT QDs Best Phosphors Previous

12 On-Chip Accelerated Aging Tests 5630 package Heatsink temperatures C Irradiance = 52 W/cm 2 Activation energy = 0.5 ev Lifetimes > 25 Khrs. possible under use conditions 12

13 On-chip QDs for Displays: Summary Narrow linewidth photoluminescent quantum dots are demonstrated in on-chip LED packages suitable for BLUs. QDs exhibit the following: - Low thermal quenching - Tolerance to high pump intensity - Tolerance to ambient packaging and operating conditions Accelerated aging indicates lifetimes >25 khrs are possible Wavelength (nm) 13

14 Thank you! Julian Osinski, Ph.D. Pacific Light Technologies 14