Norbert Frühauf
Institut für Großflächige Mikroelektronik
Universität Stuttgart
Technologische
Grundlagen aktueller
Bildschirmtrends
www.igm.uni-stutgart.de
Overview Institute for Large Area Microelectronics
The Laboratory:• Cleanroom area of 480 m2, Cleanroom Class 10 and 100
• In operation since May 1991
• Since 2011: Institute for Large Area Microelectronics
• Current Staff (September 2016: 15) plus ca. 10 students
• Max. Substrate Size: 16“x16“ (406 mm x 406 mm)
Available Equipment:• MRS Stepper and MA6-Mask Aligner (Suess) for Lithography
• UV-Laser Lithography System DWL 400 (HIMT)
• Spin tools for cleaning, development and wet etching (STEAG)
• Inline Sputter machines ZV6000 DC/RF (Leybold)
• KAI1 PECVD machine (BALZERS)
• RIE/PE dry etching reactor KAI Etch (BALZERS)
• Modified Ion Implanter for large substrate sizes (EATON)
• Excimer laser crystallization SAELC (SOPRA)
• Ink jet printer and Glove Box system for organic semiconductors
• Equipment for LC cell fabrication
• TAB (OSAKI) and Flip chip bonder FC6 (SUESS)
• Various measurement equipment
www.igm.uni-stutgart.de
Research and Development Competence
Large Area Microelectronic Systems
A-Si, µc-Si and N-, P-channel, and CMOS LTPS TFTs
Metal Oxide TFTs
Solution/Suspension processed OTFT and CNT-TFTs
CNT Electrodes, Color Filter Technology
Active Matrix LCD, OLED and EPD Displays
Rigid and flexible substrates (Glass, Metal foil, Plastic)
Adaptive Optical Elements
Bonding processes on glass and flexible substrates
Integrated Driver Electronics
FPGA Driver electronic systems
483 µm
16
4 µ
m
www.igm.uni-stutgart.de
Current Trends in Displays (specifically TVs)
● Energy Efficiency (Energy Efficiency Labels)
● Ultra High Definition (4k oder 8k)
● Color Space (REC 2020)
● High Dynamic Range (HDR10, Dolby Vision)
● AMLCD vs. AMOLED
www.igm.uni-stutgart.de
Basics Energy Efficiency Index/CategoriesEU Delegiertenverordnung 1062/2010 Reference System (EEI=1)
Power per Area 4,3224 W/dm2
Max Conversion Efficiency 200 lm/W
Max Lumen per Area 86448 lm/m2
Luminance (Lambertian Characteristic) 13765 Cd/m2
AMLCD Efficiency 0,07
Front of Screen Luminance 964 Cd/m2
A+++ < 0.1 96 Cd/m2
A++ < 0,16 154 Cd/m2
A+ < 0,23 222 Cd/m2
A < 0,3 289 Cd/m2
B < 0,42 405 Cd/m2
C < 0,6 578 Cd/m2
D < 0,8 771 Cd/m2
E < 0,9 868 Cd/m2
F < 1 964 Cd/m2
Energy Efficiency Categories:
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Electro-optical Principle of Operation
Transmissive(e.g. LCD)
Polarizer
Polarizer
Electrodes and Orientation Layer
Liquid CrystalMolecules
Electrodes and Orientation Layer
5 µm
M.Schadt
Low Driving Voltages Voltage controlled effect Light modulation Color with Color Filters
High Energy Efficiency Current controlled effect Self emitting All colors available
Ca CathodeElectron Transport and
Emission LayerHole Transport Layer
Hole Injection Layer
Substrate (Transparent)
0,5 µm
Self - Emitting(e.g. OLED)
Ch. Tang
ITO Anode
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Colored Active Matrix Liquid Crystal Panel
(Source: Spektrum der Wissenschaft)
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2 TFT + 1 C Active Matrix OLED (Brody et al.)
Most simple AMOLED pixel structure Switching-TFT plus storage capacitor Analog TFT as current source → stability and homogeneity critical
VD
D
Sel
VDa
ta
C
S
-5 ,0 E -0 6
-4 ,0 E -0 6
-3 ,0 E -0 6
-2 ,0 E -0 6
-1 ,0 E -0 6
0 ,0 E + 0 0-1 0 -5 0U D S in V
I D in
A
U _ G a te = - 4 VU _ G a te = - 5 VU _ G a te = - 6 VU _ G a te = - 7 V
-5,0E-06
-4,0E-06
-3,0E-06
-2,0E-06
-1,0E-06
0,0E+00
-10 -5 0UDS in V
I D in
A
U_ Gate = -4VU_ Gate = -5VU_ Gate = -6VU_ Gate = -7VOLED
www.igm.uni-stutgart.de
Structure of an AMOLED
Metal 1, Gate(Row Metallisation)
GateoxideDrain Source
Substrate
Bufferoxide
Isolation
Metal 2, D/S-Contacts(Column Metallization)
Top ElectrodeConnection
PlanarizingPassivation
StepCoverage Bottom
Electrode
OLEDStack
TopElectrode
Encapsulation
Gap
TopEmission
BottomEmission University of Stuttgart, 2011
(OLED Coating: Novaled)
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Color Creation Principle
LCD Color Filter
Backlight
OLED structured OLED Color Filter
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Power Efficiency of Active Matrix LCD
Effect Ideal Real
Light from Backlight: 100% 100%
Polarizer: ideal: 50% 50%real: 40% 40%
Color Filter: typ: 30% 15% 12%
Aperture: typ: 60% 9% 7%
70 % Losses by Color Filter !!!!
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Quantum Dot Backlights
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Practical Implementations QD Backlights
+ Color space
- Power efficiency
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Color Space QD Backlights
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Current Developments
Photostructurable QD Layers (e.g. Merck)
Color Filter replaced by color structured QD layers
● 3x Efficiency● In Cell Polarizer needed
Quantum Rods instead of Quantum Dots (e.g. Univ. Ghent)
Polarized Emission
● 2x Efficiency (elimination of Polarizer Losses)
T. Augbert et al., Large Scale and Switchable Polarized Emission From Semiconductor Nanorods Aligned in Polymeric Nanofibers, Eurodisplay 2015, S2.4
www.igm.uni-stutgart.de
Color Space Samsung OLED Tablet
(Source: S. Schimpf, University of Stuttgart)
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Efficiency Improvement OLEDs
● Always only Light on Demand
● New Concepts for efficient Light Generation
S. Sato, „Organic LED with low power consumption and long lifetimes, SPIE Newsroom, 10.1117/2.1201608.006688
e.g. Exiplex Triplet Energy Transfer (Semiconductor Energy Laboratory, Japan)
www.igm.uni-stutgart.de
Luminance and Contrast Properties
LCD
Viewing angle dependence Typ. Contrast < 1000:1 Luminance defined by backlight
OLED
No viewing angle dependence Typ. Contrast > 100.000:1 Luminance several hundred Cd/m^2
(Lifetime limited !)
www.igm.uni-stutgart.de
Visual perception and High Dynamic Range
Quelle: Helge SeetzenFa. BrightSide
Logarithmic Luminance in cd/m2
Simultaneous Vision Range
Adaptation Range
Displays
www.igm.uni-stutgart.de
HDR 10 vs. Dolby Vision
HDR 10 Dolby Vision
Bit Depth 10 bits/color 12 bits/color
High Brightness 1000 nits(or ≥ 540 für OLEDs)
4000 nits (Mastering bis 10000 nits)
Low Brightness ≤ 0.05 nit (or ≤ 0,0005 nits for OLEDs)
≤ 0,004 nits(Mastering bis 0,0001 nits)
Min. Contrast 20000:1 (or 108000 for OLEDs)
1000000:1 for full content
(adapted from Mathew Brennesholz, „HDR 10 versus Dolby Vision“, Mobile Display Monitor 12 August 2016)
www.igm.uni-stutgart.de
High Dynamic Range LCD
•Contrast typvically several 100:1
• Much lower considering:
➢ Wider viewing angles➢ Wavelength dependence
• Overall Screen Luminance:
Backlight luminance x Modulator Transmission
• Idea for HDR Display (H. Seetzen, ca. 2003):
Put LCD plus modulated backlight in series to achieve 105 :1
www.igm.uni-stutgart.de
Dynamic/Adaptive Backlight
Courtesy: H. Seetzen
BacklightBacklight LCDLCDImageImage Output imageOutput image
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Drive LED
Importance of Glare Spread Function
Courtesy: H. Seetzen
Receive ImageReceive Image
Drive LED
Divide Image byLED light field to obtain LCD values
Receive Image
Drive LED
Divide Image byLED light field to obtain LCD values
Output Luminanceis the product of LED light field andLCD transmission(Problematic error)
Oops
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Importance of Glare Spread Function
Courtesy: H. Seetzen
Veiling Luminance masks imperfection
But: ➢ Issues if LCD contrast variations !!!!➢ High cost for high resolution backlight for Large Screen Sizes
www.igm.uni-stutgart.de
Alternative Possibility for HDR LCD
(Source: Display Search)
• Two full resolution LCD in series (one bw without Color filter) might be
cheaper than high resolution LED backlight
● Cell without Color Filter and only one polarizer < 15 % of total Sales Cost (today well below 300 Euro for 40 inch)
● Panasonic just announced such a Dual layer LCD with C > 1.000.000:1
www.igm.uni-stutgart.de
Flexible OLED Demonstrators
(Source: Sony, 2010)(Universität Stuttgart, 2011)
www.igm.uni-stutgart.de
Flexible LCD with CNT Electrodes, Universität Stuttgart, 2008
Flexible LCD Demonstrator
www.igm.uni-stutgart.de
Ultra Thin Glass LCD Demonstrator
Thin Glass AMLCD(Worldwide First)
~10mm
75m Substrate
S. Höhla, S. Garner, M. Hohmann, O. Kuhls, X. Li, A. Schindler, N. FrühaufFirst Prize: Active matrix color LCDs on ultra thin glass substratesProceedings of Electronic Displays Conference, Paper 16.2 (2011)
www.igm.uni-stutgart.de
EU/BMBF OLEA+ LiCRa Project Plastic LCD Demonstrator
phone +49 (0) 711 685-
fax +49 (0) 711 685-
University of Stuttgart
Thank you!
Prof. Dr.-Ing. Norbert Fruehauf
• 66924
•
Institute for Large Area Microelectronics
Allmandring 3B, D-70569 Stuttgart, Germany
Web: www.igm.uni-stuttgart.de
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