Advanced OLED Microdisplays for Near-To-Eye Applications

Advanced OLED microdisplays for near-to-eye applications

Uwe Vogel1*, Bernd Richter1, Philipp Wartenberg1, Peter König1, Olaf Hild1, Karsten Fehse1, Matthias Schober1, Elisabeth Bodenstein2

1 Div. Microdisplays & Sensors 2 Div. Electron Beam * Corresponding author: [email protected]

Fraunhofer Institute for Organic Electronics, Electron Beam and Plasma Technology FEP, Dresden, D-01109, Germany

Dr. Uwe Vogel [email protected] Fraunhofer FEP

Dr. Uwe Vogel [email protected] Fraunhofer FEP Core Competencies

ELECTRON BEAM PLASMA-ACTIVATED TECHNOLOGY HIGH-RATE DEPOSITION

SPUTTERING HIGH-RATE PECVD TECHNOLOGY

TECHNOLOGIES FOR IC AND ORGANIC ELECTRONICS SYSTEM DESIGN

Dr. Uwe Vogel [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

Dr. Uwe Vogel [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.

Dr. Uwe Vogel [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

Dr. Uwe Vogel [email protected] OLED microdisplay challenges

Dr. Uwe Vogel [email protected] State-of-the-art OLED display color-patterning technologies

White OLED with color-filter (CF) EML patterning by shadow masking

encapsulation encapsulation CF Red CF Green CF Blue cathode cathode ETL ETL

W-EML R-EML G-EML B-EML

HTL HTL Anode R Anode G Anode B Anode R Anode G Anode B CMOS Wafer CMOS Wafer

+ Simple process + Wide color gamut + Homogeneous alteration + High contrast  Low efficiency  Low resolution (<600ppi as of today)  Color diffusion  Limited scaleability  Differential aging All commercial OLED microdisplays as of today

Dr. Uwe Vogel [email protected] Comparison of OLED patterning technologies

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 resists, low-viscosity inks, functional Capillary molding 50 nm X organics SAM, thin metals, org. & anorg. Soft Printing ~0.1-2 µm X semiconductors Inkjet Printing ~ 10-20 µm Small-molecules and polymers Panasonic Flash-mask transfer ~10 µm Small-molecules only Von Ardenne lithography Photolithography ~1 µm Resists, functional organics Fraunhofer FEP

Electron-beam direct write ~ 1 µm Organics and inorganics Fraunhofer FEP

Dr. Uwe Vogel [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 Electron energy dose • 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 500 µm • Energy can be deposited in layers underneath the encapsulation layers without destroying the encapsulation itself • Individual organic layers can be directly targeted

Dr. Uwe Vogel [email protected] 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

Dr. Uwe Vogel [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 Electron Beam patterning in cooperation with Raith GmbH ppi • Writing time: 105 s

Dr. Uwe Vogel [email protected] High-resolution patterning by electron beam direct-write

• Application examples: • Signage - Micro and miniature displays, large-area • Emissive measuring devices custom-designed lighting components, emissive such as rulers and yardsticks tattoos / eSkin • Data Storage applications • Integrated security features (PUFs – physically unclonable functions) - emissive passport photos

Dr. Uwe Vogel [email protected] OLED microdisplay challenges

Dr. Uwe Vogel [email protected] Bi-directional OLED microdisplay

SVGA

Dr. Uwe Vogel [email protected] Bi-directional OLED-on-silicon microdisplays 16

 no imaging optics so far

Dr. Uwe Vogel - Confidential - [email protected] Bi-directional OLED-on-silicon microdisplays 17

 Feedback-mode demonstrator  no imaging optics so far

Dr. Uwe Vogel - Confidential - [email protected] Bi-directional OLED microdisplay

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

Line-of-sight

Dr. Uwe Vogel [email protected] 21 Bi-directional OLED microdisplays for eye-controlled interactive smart glasses

 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

Dr. Uwe Vogel [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

Dr. Uwe Vogel [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

Dr. Uwe Vogel [email protected] Microdisplay Power Consumption

Bidirectional OLED microdisplay: - 0,6“ 800 x 600, 16μm pixel pitch - full color @ 200nits - with embedded image sensor

full screen on 200mW

Ultra-low-power microdisplay: - 0.2“ 304 x 256, 12um pixel pitch - monochrome green @ 600nits display power

3mW

Dr. Uwe Vogel [email protected] Conclusion & Outlook 27

 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

Dr. Uwe Vogel [email protected] SID Mid-Europe Chapter Spring Meeting 2017 28

 http://www.fep.fraunhofer.de/sidme17

 Program Committee/Key notes:  ZEISS  Intel  Microsoft  Microoled  Kopin  Sony  Volkswagen  Univ. of Cambridge  Univ. of Edinburgh  …

Dr. Uwe Vogel [email protected] Contact 29

 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

Dr. Uwe Vogel [email protected]