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Although it is possible to print many different kinds of electronic displays, in order for them to be commercially successful, they must be robust enough to survive for the necessary time and conditions required of the display. This condition has been a limitation of many printable electronic displays. Beyond printability and functionality, one of the most important requirements is encapsulation. Many of the materials used in printed electronic displays are chemically sensitive, and will react with many environmental components.
This concise and highly targeted report from IDTechEx technology analyst Dr Harry Zervos gives an in-depth review of the issues, as well as forecasts for OLEDs and OPV, in order to understand the influence that the development of flexible barriers will have on the mass deployment and adoption of flexible electronics and photovoltaics.
A large opportunity lies in the development of devices in a flexible form factor, allowing them to be more robust, lightweight and versatile in their use.
However, many of the materials used in OLED displays and organic photovoltaics are sensitive to the environment, limiting their lifetime. These materials can be protected using substrates and barriers such as glass and metal, but this results in a rigid device and does not satisfy the applications demanding flexible devices. Plastic substrates and transparent flexible encapsulation barriers can be used, but these offer little protection to oxygen and water, resulting in the devices rapidly degrading.
In order to achieve device lifetimes of tens of thousands of hours, water vapor transmission rates (WVTR) must be 10-6 g/m2/day, and oxygen transmission rates (OTR) must be < 10-3 cm3/m2/day. For Organic Photovoltaics, the required WVTR is not as stringent as OLEDs require but is still very high at a level of 10-5 g/m2/day. These transmission rates are several orders of magnitude smaller than what is possible using any plastic substrate, and they can also be several orders of magnitude smaller than what can be measured using common equipment designed for this purpose. For these (and other) reasons, there has been intense interest in developing transparent barrier materials with much lower permeabilities.
This concise and unique report from IDTechEx gives an in-depth review of the needs, emerging solutions and players. It addresses specific topics such as:
Companies which are active in the development of high barrier films and their achievements on the field to date.
Surface smoothness and defects (such as cracks and pinholes) and the effect that these characteristics would have on the barrier behavior of the materials studied.
Traditional methods of measurement of permeability are reaching the end of their abilities. The MOCON WVTR measurement device, which has been an industry standard, cannot give adequate measurements at the low levels of permeability required for Organic Photovoltaics and OLEDs. Other methods of measurement and equipment developed are being discussed.
Forecasts for OLEDs and OPV, in order to understand the influence that the development of flexible barriers would have at the mass deployment and adoption of these technologies.
For those developing flexible electronics, seeking materials needs and opportunities, this is a must-read report.
2. INTRODUCTION TO ENCAPSULATION
3. SURFACE SMOOTHNESS – DEFECTS
3.1. Important considerations of surface smoothness
3.2. Micro Defects
3.2.1. Crystalline regions
3.2.3. Smoothness / Cracks-Scratches
4.2. Alcan Packaging
4.4. Fraunhofer – POLO Alliance
4.6. Tera Barrier
4.8. Other technologies – High barrier adhesives
4.9. Best performing barriers developed to date
5. BARRIER MEASUREMENTS
5.1. The Calcium test
5.3. Illinois Instruments
5.4. Fluorescent Tracers
5.5. Black Spot Analysis
5.6. Tritium Test
5.10. Mass Spectrocopy – gas permeation (WVTR & OTR potential applications)
5.11. Standardization efforts
6. FORECASTS FOR BARRIER FILMS FOR FLEXIBLE ELECTRONICS 2011-2021
6.1. The potential significance of organic and printed inorganic electronics
6.2. Forecasts for flexible electronics 2011-2021
6.3. Barrier films market size
APPENDIX 1: ATOMIC LAYER DEPOSITION
APPENDIX 2: GLOSSARY
APPENDIX 3: IDTECHEX PUBLICATIONS AND CONSULTANCY
2.1. Water vapor and oxygen transmission rates of various materials.
2.2. Requirements of barrier materials
3.1. Oxygen transmission rates of polypropylene with various coatings.4, 7
4.1. Overview of promising high barrier technologies
5.1. Lower detection limits of several barrier performance measurement techniques
5.2. Metrics and standards for organic solar cell components42
6.1. Leading market drivers 2021
6.2. Market value (US$ billion) of flexible/conformal electronics 2011-2021
6.3. Total market value of flexible vs. rigid electronics 2011-2021
6.4. Barrier Layer Market Forecasts 2011-2021
1.1. Examples of flexible OLED displays by SONY and AddVision
1.2. Flexible OLED fabricated using IMRE’s high barrier substrate and encapsulation technique44
1.3. Flexible Solar Cell developed by Fraunhofer IPMS
2.1. Schematic diagrams for encapsulated structures a) conventional b) laminated c) deposited in situ4
2.2. Scanning electron micrograph image of a barrier film cross section6
3.1. Visual defects of a selection of materials with barrier films highlighted through calcium corrosion test. Optical microscope magnification 10x.44
3.2. SEM pictures of the Atmospheric Plasma Glow Discharge deposited silica-like films on polymer substrates. Left: Film with embedded dust particles . Right: uniform film27
3.3. OTR as a function of defect density, the correlation between defect density and the oxygen transmission rate
3.4. SEM image of a pinhole defect formed from a dust particle32
3.5. Scanning electron microscope image of ITO coated on parylene/polymer film34
3.6. The measurement of OLED’s lifetime of SiON/PC/ITO and SiON/parylene/PC/parylene/ITO substrate34
4.1. Calcium test results demonstrating superior WVTR performance
4.2. 3M barrier film development roadmap
4.3. ALCAN Packaging flexible barrier based on PET and SiOx47
4.4. DuPont Displays technology pipeline
4.5. Scanning electron micrograph of a thin hybrid polymer coating on SiOx deposited on a flexible PET film 46
4.6. OTR values achieved with different POLO multilayers46
4.7. Schematic of cross section of graded barrier coating and complete barrier film structure1.
4.8. Examples of polymer multi-layer (PML) surface planarization a) OLED cathode separator structure b) high aspect ratio test structure.3, 8
4.9. Vitex multilayer deposition process8.
4.10. SEM cross section of Vitex Barix material with four dyads.
4.11. Optical transmission of Vitex Barix coating8.
4.12. Edge seal barrier formation by deposition through shadow masks10.
4.13. Three dimensional barrier structure. Polymer is shown in red, and oxide (barrier) shown in blue10.
4.14. Schematic of flexible OLED with hybrid encapsulation31
4.15. Area sealing55
4.16. DELO’s light curing adhesive solution for electrophoretic displays55
4.17. Performance characteristics of DELO’s light-curing materials55
4.18. Specifications on WVTR for different applications, as seen by Vitex Systems36
4.19. 3M specifications on WVTR and OTR for high barrier applications with stringent requirements 14
5.1. 2.25 mm2 area of a 50 nm layer of Ca deposited onto barrier coated PET viewed through the substrate. i. Image after 1632 h of exposure to atmosphere; ii. Image analysis whereby the grey scale of Ca degradation is processed to yiel
5.2. A simple set-up for measuring optical transmission of calcium test cells48
5.3. MOCON’s Aquatran™ Model 138
5.4. MOCON’s Aquatran™ schematic38
5.5. MOCON’s OX-TRAN® Model 2/1039
5.6. Silica induced black spots, letters A & B mark black spots with a centralized black dot (silica particle)32
5.7. Black spot formation and growth mechanisms 32
5.8. General Atomics HTO WVTR testing apparatus40
6.1. Market value (US$ billion) of flexible/conformal electronics 2011-2021
6.2. Total market value of flexible vs. rigid electronics 2011-2021
6.3. Barrier Layer Market Forecasts 2011-2021
6.4. Size of opportunity
7.1. The iRex iLiad and the Amazon Kindle rigid e-book readers
7.2. PVI’s flexible electrophoretic display and color electrophoretic display by SAMSUNG LCD, demonstrated at SID 2008