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© Fraunhofer FEP
Dr. Uwe [email protected]
Advanced OLED microdisplays for near-to-eye applications
Fraunhofer Institute for Organic Electronics, Electron Beam and Plasma Technology FEP, Dresden, D-01109, Germany
Uwe Vogel1*, Bernd Richter1, Philipp Wartenberg1, Peter König1, Olaf Hild1, Karsten Fehse1, Matthias Schober1, Elisabeth Bodenstein2
1 Div. Microdisplays & Sensors2 Div. Electron Beam
* Corresponding author: [email protected]
© Fraunhofer FEP
Dr. Uwe [email protected]
Fraunhofer FEP Core CompetenciesELECTRON BEAM TECHNOLOGY
SPUTTERING TECHNOLOGY
PLASMA-ACTIVATED HIGH-RATE DEPOSITION
HIGH-RATE PECVD
TECHNOLOGIES FOR ORGANIC ELECTRONICS
IC AND SYSTEM DESIGN
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Dr. Uwe [email protected]
Introduction: The case for OLED microdisplays in NTE
OLED-on-Silicon technology
Highly efficient light source and imager in one (emissive microdisplay)
Low-power
High contrast
No backlight-related virtual screen for see-through (ST)
Smallest system footprint
high-resolution & -accuracy patterning
Pixel pattern determined by CMOS photolithography
OLED pixel density >1,000..5,000..10,000ppi
arbitrary emission shapes
fast response time (MHz)
electronics feature integration
driving, control, processing
CMOS sensor co-integration and acquisition
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Dr. Uwe [email protected]
Introduction: Microdisplay challenges in ST-NTE applications
Sun-light conditions
high-brightness (>5,000 cd/m²)
Lifetime
regularly accompanied by elevated temperature operation
lowest pixel pitch, directly correlating to die size and cost
Limited by voltage drive requirements for high-brightness (OLED LIV)
low-power operation for long battery life,
affected by OLED efficiency and backplane architecture,
extended color gamut,
embedded modes for user interaction, e.g., embedded sensors and emission/detection outside the visible.
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Dr. Uwe [email protected]
OLED microdisplay challenges
How to address those challenges?
OLED micro-patterning
Electron-beam direct-writing
Embedded sensors, spectral characteristics
Bi-directional OLED microdisplay
Backplane architecture
DRAM vs. SRAM
© Fraunhofer FEP
Dr. Uwe [email protected]
OLED microdisplay challenges
How to address those challenges?
OLED micro-patterning
Electron-beam direct-writing
Embedded sensors, spectral characteristics
Bi-directional OLED microdisplay
NIR/UV emission
Backplane architecture
DRAM vs. SRAM
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Dr. Uwe [email protected]
State-of-the-art OLED display color-patterning technologies
White OLED with color-filter (CF) EML patterning by shadow masking
+ Simple process+ Homogeneous alteration Low efficiency Color diffusion
All commercial OLED microdisplays asof today
+ Wide color gamut+ High contrast Low resolution (<600ppi as of today) Limited scaleability Differential aging
CMOS Wafer
HTL
ETLcathode
encapsulation
Anode R Anode G Anode B
W-EML
CF BlueCF GreenCF Red
ETLcathode
encapsulation
CMOS WaferAnode G Anode BAnode R
HTL
R-EML G-EML B-EML
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Approach Resolution Compatibility proven
Fine metal masking 30 µm Small-molecules only Samsung
Vapor Jet 40 µm Small-molecules only UDC
LIFT 3 µm Small-molecules only Samsung / 3M
LITI 40 µm Small-molecules and polymers Samsung / 3M
Imprint Lithography ~10 nm moldable resists, functional organics X
Capillary molding 50 nm resists, low-viscosity inks, functional organics X
Soft Printing ~0.1-2 µm SAM, thin metals, org. & anorg. semiconductors X
Inkjet Printing ~ 10-20 µm Small-molecules and polymers Panasonic
Flash-mask transfer lithography ~10 µm Small-molecules only Von Ardenne
Photolithography ~1 µm Resists, functional organics Fraunhofer FEP
Electron-beam direct write ~ 1 µm Organics and inorganics Fraunhofer FEP
Comparison of OLED patterning technologies
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Dr. Uwe [email protected]
OLED emission modification by electron-beam (EB) direct-write
• Goal: high-res (1..10µm) EB-induced EML/OLED patterning• Achieved so far: Emission of OLED can be individually modified by
EB process after encapsulation
• penetrating electrons of EB leads to local reduction in charge carrier injection, which permanently reduces the local emission level
• electron dose defines degree of dimming
• reduced local emission + conductivity
• Electron energy determines their penetration depth into the OLED layer stack
• Energy can be deposited in layers underneath the encapsulation layers without destroying the encapsulation itself
• Individual organic layers can be directly targeted
Electron energy dose
500 µm
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Simulation of electron energy absorbed in OLED layer stack
• Estimation of penetration depth and energy absorption of the electrons in the OLED stack by Monte Carlo simulations specific layer properties and scattering processes at interfaces must be taken into account
• Majority of the energy is absorbed in the encapsulation layers and only a fraction reaches the delicate organic layers
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Dr. Uwe [email protected]
High-resolution patterning by electron-beam direct-write
• Lateral control of the electron beam and pixel-by-pixel adjustment of the grey-value enables high-resolution direct-write patterning
• Design example: Picture of Semperoper Dresden
• Image size: 1,8 x 1,2 mm2
• Resolution: 2 μm / 12.700 ppi
• Writing time: 105 s
Electron Beam patterning in cooperation with Raith GmbH
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High-resolution patterning by electron beam direct-write
• Application examples: • Signage - Micro and miniature displays, large-area
custom-designed lighting components, emissive tattoos / eSkin
• Integrated security features (PUFs – physically unclonable functions) - emissive passport photos
• Emissive measuring devices such as rulers and yardsticks
• Data Storage applications
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Dr. Uwe [email protected]
OLED microdisplay challenges
How to address those challenges?
OLED micro-patterning
Electron-beam direct-writing
Embedded sensors, spectral characteristics
Bi-directional OLED microdisplay
Backplane architecture
DRAM vs. SRAM
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Dr. Uwe [email protected]
- Confidential -
16Bi-directional OLED-on-silicon microdisplays
no imaging optics so far
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Dr. Uwe [email protected]
- Confidential -
17Bi-directional OLED-on-silicon microdisplays
Feedback-mode demonstrator no imaging optics so far
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Dr. Uwe [email protected]
• Adds eye/gaze-controlled (i.e., hands/voice-free) interactivity to smart glasses
• Enables vergence monitoring
Bi-directional OLED microdisplay
Line-of-sight
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Glass@Service: „Interactive personalized visualization in industrial processes as part of Digital Factory in electronics manufacturing“
Funded within „Smart Service World“ of BMWi, started Mar‘16
Bi-directional OLED microdisplays for eye-controlled interactive smart glasses21
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Dr. Uwe [email protected]
OLED microdisplay challenges
How to address those challenges?
OLED micro-patterning
Orthogonal photolithography
Electron-beam direct-writing
Embedded sensors, spectral characteristics
Bi-directional OLED microdisplay
NIR/UV emission
Backplane architecture
DRAM vs. SRAM
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Dr. Uwe [email protected]
Microdisplay Backplane Architecture For NTE long battery life often more
important than frame rate/resolution
display simple graphics (e.g., symbols) and text
alteration frequency of screen content low (<5Hz)
image data stored in a static random access memory SRAM-like pixel cell architecture
Direct serial pixel-wise addressing scheme enables much lower bandwidth for display interface
strong reduction of display power by minimizing backplane consumption
OLED power/efficiency determines overall power consumption now
Even VIDEO power advantage for moderate frame rates and resolution
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Dr. Uwe [email protected]
Microdisplay Power Consumption
Bidirectional OLED microdisplay:- 0,6“ 800 x 600, 16μm pixel pitch- full color @ 200nits- with embedded image sensor
Ultra-low-power microdisplay:- 0.2“ 304 x 256, 12um pixel pitch- monochrome green @ 600nits
full screen on
dis
pla
y p
ow
er
3mW
200mW
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Dr. Uwe [email protected]
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Challenges for OLED microdisplays in near-to-eye applications Full-color high-brightness, High-temperature, Lifetime, Minimum pixel pitch,
Low-power consumption, long battery life, Wide color gamut, User Interaction
Approaches to address OLED micro-patterning
Photolithography Lift-off: general yield issues (Dry) Etching: under evaluation
Electron-beam direct-writing Fixed images at 2μm shown micro-signage R,G,B-subpattering under evaluation
Embedded sensors, extended spectral characteristics Bi-directional OLED microdisplay gaze-interactivity for NTE NIR/UV emission non-VIS NTE; fluorescence sensors, optogenetics
Backplane architecture SRAM for low-power NTE
Conclusion & Outlook
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Dr. Uwe [email protected]
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http://www.fep.fraunhofer.de/sidme17
Program Committee/Key notes: ZEISS IntelMicrosoftMicrooledKopin SonyVolkswagen Univ. of CambridgeUniv. of Edinburgh…
SID Mid-Europe Chapter Spring Meeting 2017
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Dr. Uwe [email protected]
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Dr. Uwe Vogel Head of Division OLED Microdisplays and Sensors Deputy Director Fraunhofer Institute for Organic Electronics, Electron Beam and Plasma Technology FEP
Maria-Reiche-Strasse 2 D-01109 Dresden phone:+49-351-8823-282 email: [email protected]
Acknowledgements Dr. Alexander Zakhidov, Texas State University
Work was in parts sponsored by European Commission within the HYPOLED project (High-Performance OLED-Microdisplays for Mobile Multimedia HMD and Projection
Applications, ICT-2007.3.2-217067) Federal Ministry for Education and Research of the German government (Bundesministerium für Bildung und Forschung), BMBF 01 BK
916-919, 16SV2283/"ZOOM", 16SV3682/"ISEMO“, 16SV5036 “NIR-OLED” Sächsische Aufbaubank (SAB) of the State of Saxony (11107/1733 “A18HVMOS” & 100070897 “Cool Projector”) Fraunhofer Internal Programs “iSTAR” Grant No. WISA 817 805, “3D Signage” Grant No. MAVO 823279, “OLITH” Grant No. ATTRACT
162-600032
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