Progress in Display and Lighting Technologies TANG Ching Wan ( 鄧青雲 ) Department of Chemical Engineering University of Rochester (Formerly with Kodak Research Laboratories, 1975 2006)
Introduction: 元朗 Electrical Grids Yuen Long in 1960 s 祠堂 Village shrine
Display Technologies & Status Cathode Ray Tube (CRT) Liquid Crystal Display (LCD) Plasma Display (PDP) Organic Light Emitting Diode (OLED) Electrophoretic Display (E book) Others Vanishing Dominating Shrinking Emerging Rapidly growing Gone or to be recycled Some historical milestones
Cathode Ray (indicator) Tube CRT Karl F. Braun Built in 1897 Deflection of electron beam Electron beam striking a luminescent screen produces indicator light Nobel Prize 1909 for inventing telegraph
Today s colored CRT TV Today s PDP CRT TV Chevallier, 1929 Patterned phosphor screen Sweeping single e beam CRT depth ~ Screen size Bulky and heavy First Pattern 42 Full phosphor Color PDP TV screen was produced Multiple in localized 1996 (Fujitsu) excitation Screen is depth independent Thin and light
Liquid Crystal Display (LCD) Discoveries at the RCA Sarnoff Laboratories: 1962: R. Williams discovered the phenomenon of Williams Domains in nematic LC 1968: G. Heilmeir demonstrated dynamic scattering LCD clock 1970: First LCD Watch by Optel Domains in liquid crystals with an applied field of 2,500 V/cm
Twisted nematic liquid crystals M. Schadt and W. Helfrich LC materials Hoffmann La Roche Appl. Phys. Lett. 18, 127 (1971) Cyanobiphenyls (1972) G. Gray, J. Nash and K. Harrison Electro optical effect allowing variations of the rotation of linearly polarized light continuously from 0 to 90.
Today s Active Matrix AMLCD Gate or row electrode Common electrode Color filter a-si TFTs ITO TFT substrate Polarizer 240 µm Backlight Diffuser Polarizer Data or column electrode Gate or row electrode LC Common substrate Each pixel is independently driven by a thin-film transistor (TFT)
World s Largest LCD TV: 108 Diagonal Sharp Electronics (2008)
Generation 10 Motherglass Size: 2.85m x 3.05m Amazon price Sharp Corp
Projection
Remaining Technical Challenges for LCD Displays: Response time: 5 ms <1 ms Sunlight readability Lower power consumption Reduced d color shift Slimness & lightweight Lower cost Notes from ST Wu, UCF
LCD: Optical Efficiency Transmittance ~ 5% Analyzer: 90% Color Filters: 30% Wide view LC: 85% TFT Array: 60% Polarizer: 45% Optical films: 70% Backlight YB Huang, IDRC 2008 Notes from ST Wu, UCF
Backlight and Color Gamut CFs, CCFL, LED CIE 1976 Chromaticity CCFL LED 400 450 500 550 600 650 700 Most NB & LCD monitors use LED BLU R. Lu et al, Opt. Express 14, 6243 (2006) 14/55 Notes from ST Wu, UCF
Backlight Units LED penetration Source: Displaysearch
Samsung s 15 BP LCD Prototype SID 08 Exhibition SID 09 Exhibition 1. Fast switching time <1 ms Color sequential w/o CFs 2. No alignment layers Simple process & lower cost 3. Isotropic dark state: High CR & wide view w/o optical films 4. Cell gap insensitivity Samsung plans for mass production in 2011 Notes from ST Wu, UCF
TV Market Forecast DisplaySearch: Q4, 2008 2009: LCD/PDP/CRT~73/15/12
LCD Incident randomly polarized light OLED Backlight Diffuser Film v Backlight Enhancement Film Rear Polarizer Compensation film ETL HTL Glass Glass Substrate Transparent Electrode Alignment Layers Transparent Electrode Glass Substrate Compensation film Front Polarizer anti scratch, anti glare, and anti reflection coatings LC v Key OLED advantages: Higher image quality Lower power consumption Lower cost structure Cost of materials: Backlight + color filter + polarizer ~ 40 50% of a LCD display
Potential cost reduction in OLED Information Display October/07 Information Display October/07 DuPont OLEDs
HTL (60nm) ETL (60nm) Mg:Ag Appl. Phys. Lett. 51, 913 (1987) Organic electroluminescent diodes CW C.W. Tang and dsa S.A. Van Slyke H 3 C ITO ~ 0.8 ev ~ 0.3 ev CH 3 CH 3 Alq N N CH 3 Diamine N O O Al N O N Key features: HTL/ETL bi layer structure Vapor deposited molecular thin films Ohmic contacts High injection current Low drive voltage High brightness/efficiency Fast response Lambertian emission/wide view angle µ h ~ 10 3 cm 2 /Vs µ e ~ 10 6 cm 2 /Vs
HTL (60nm) ETL (60nm) J. Appl. Phys. 65, 3610 (1989) Electroluminescence of doped organic thin films; Tang, VanSlyke, Chen Mg:Ag S N Et N O O Et NC C540 CN ITO H 3C N CH 3 O CH 3 DCM1 H 3 C CH 3 CH 3 N N CH 3 N O O Al N N O Alq N CN NC O CH 3 DCM2 Host Dopant
Complex Layer Structure to Control Charge and Exciton Movement S T e mbination Recom h + T From D. Giesen (Kodak)
Active matrix OLED pixel circuits: Circuit without V th compensation Circuit with V th compensation Data Line VDD Select Line Driving TFT Switching TFT AZ (auto zero) AZB OLED Dawson, et al. SID 99 Digest, P438.
LG s 15 OLED TV at CES 2009
Samsung s prototype 40 a Si OLED TV (2005)
OLED Hand held Products: Samsung Rogue cell phone Microsoft Zune MP3 player Nikon S70 camera
SONY OLED TV (Model XEL1) Introduced in Japan: Dec/2007 11 screen 3 mm thick
Sony 27 OLED TV Laser thermal dye transfer patterning process to produce RGB color pixels
OLED Display Revenue Forecast by DisplaySearch, Q3 09
Flexible OLED display by UDC/LGD(2008) Durable and Flexible OLED Display Demonstration by Samsung (2009)
E books: Amazon, Sony, Prime View (E ink), Plastic Logic Amazon s Kindle, current price : US$ 259.0 6 Store many books Thin, light, and long battery life Variable fonts Readable in sunlight
Electrophoretic Displays: Movement of charged particles inside a micro capsule Micro capsules Pros: Paper like display Low power consumption Cons: Low switching speed Limited video and colors
Lighting Technologies Incandescent Fluorescent LED / OLED To be phased out? Will be around for a long time Will light up the future?
2008 Data: Total US energy consumption ~ 100 quads (=10 17 BTU) Electricity generation accounts for ~ 40 % Lighting accounts for ~ 20% of electricity generation 2001 Data http://apps1.eere.energy.gov/buildings/publications/pdfs/ssl/ssl_mypp2009_web.pdf
Lighting Technologies Incandescent Fluorescent and Compact Fluorescent LED Lighting Compact i LED (CREE LR6) o LED 1,000 h 15 lm/w Inefficient i 10,000 h 70 lm/w Poor CRI Toxic 50,000 h 100 lm/w Directional Very expensive >10,000 h > 50 lm/w Planar Not ready
The Cost of Lamp in USA Lamp Type Cost per kilolumen Incandescent Lamp (60W) $0.30 Compact Fluorescent Lamp (13W) $2 Fluorescent Lamp (F32T8 32W) $4 Integrated LED Lamp p( (18W) $150 http://apps1.eere.energy.gov/buildings/publications/pdfs/ssl/ssl_mypp2009_web.pdf
Current i LED Lamp Cost Street Prices Samsung 40 LED TV Street price: $ 1500
Cost of Light Comparison
LUXEON Rebel ES 1 Watt LED 100 lumen /watt Neutral white 4100K nerated W Heat ge Heat generation vs. input power Eff ~ 25% W/W Color spectrum Input power W Luminous efficacy vs. forward current Source = http://www.philipslumileds.com/pdfs/ds61.pdf Current (ma)
White OLED Efficacy Projection Phosphorescent Fluorescent Target Fluorescent Incandescent Source: UDC
High Performance White OLED Tandem structure Key Features: ORANGE RED Cathode EIL ETL Phosphorescent Red Phosphorescent Green EBL 1 Phosphorescent EBL 2 EL Unit Eff: 66lumen/Watt HTL HIL CCT: 3691 K EIL CRI: 85% ETL BLUE Fluorescent EL Unit Scattering layer Fluorescent Blue HTL HIL SRL Anode IES Glass Substrate Source: Y.S. Tyan, Kodak
OLED Lighting Demonstrations Osram desk light GE OLED lighting FLYING FUTURE OLED CONCEPT LIGHTING
A city of light and a fountain for the technologies of light