Advanced OLED microdisplays for near-to-eye … Symposium... · Advanced OLED microdisplays for...

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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]

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Fraunhofer FEP

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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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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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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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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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NIR/UV emission


DRAM vs. SRAM

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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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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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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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DRAM vs. SRAM

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SVGA

SVGA

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- Confidential -

16Bi-directional OLED-on-silicon microdisplays

no imaging optics so far

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- Confidential -

17Bi-directional OLED-on-silicon microdisplays

Feedback-mode demonstrator no imaging optics so far

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• Adds eye/gaze-controlled (i.e., hands/voice-free) interactivity to smart glasses

• Enables vergence monitoring


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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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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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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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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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 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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