lowering barriers to higher barriers - 201402

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For Distribution to Flexible & Printed Electronics Conference attendees only. Content remains property of FlexTech Alliance Lowering Barriers to Higher Barriers Lowering Barriers to Higher Barriers The purpose, potential and progress in barrier films or encapsulation systems for OLED — February 2014

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For Distribution to Flexible & Printed Electronics Conference attendees only. Content remains property of FlexTech Alliance

Lowering Barriers to Higher BarriersLowering Barriers to Higher Barriers

The purpose, potential and progress in barrier films or encapsulation systems for OLED — February 2014

For Distribution to Flexible & Printed Electronics Conference attendees only. Content remains property of FlexTech Alliance

Outline of Encapsulation TopicsContext: bankability and no(know)opolyWhy encapsulation is important for flexible electronics§ Protections and poisons (oxygen, UV et cetera)§ Fabrication (preparation) and adhesion§ Operation and performance (optics)§ Formation, flexibility and elasticityHow barrier technologies developed § Evolution and variations§ Evaluation and potentials§ ExpectationsWhom is doing what and why§ Encapsulation§ LaminationConclusion: readings and resources

1/8/14David Barnes 2

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Overview: The Purpose of Barrier FilmsImpede permeation of Oxygen or other solutes into electrical or optical films:§ Protect device from damage§ Preserve performanceLike insurance, specifications are complicated and you know what you really have only after you need/claim the policy.Like insurance, it is a balance between what you think you need and what you can afford.

David Barnes 1/8/14 3

Water Vapor Transmission Rate or WVTR of 10-6 g m-2 day-1

(or E-6 for short) can oxidize several monolayers of cathode film in 50,000 hours.

Oxygen Transmission Rate (OTR) of 10-4 cc(atm) m-2 day-1 can be as destructive but we worry more about WVTR because of humidity (or coffee?).

Other solutes may be critical…

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Overview: Ideal Barrier FilmsWe want… But it can’t be…Flexible film Difficult to form or apply Impervious film Invasive or conductiveTransparent film Refractive or UV sensitiveAdhesive (not delaminating) film Highly stressful for other filmsHigh availability and quality High priced or too generic

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§ Finding the right blend of materials and methods takes time.§ Few of the materials or methods used for mass-market

packaging are good enough for organic electronics.

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Bankability and No(know)opolyExperience from several barrier business valuations and transactions teaches two things§ Bankability will be less of a factor than it was in solar

§ Even OELighting will have shorter expected lifetimes§ Most OLED products are goods, not investments

§ No(know)olopy will remain an apt description of the market§ Suppliers will adjust prices based on perceived risk§ Customers will adjust specs based on perceived cost§ Both will find barrier reliability difficult to quantify§ No one will know product lifetimes anytime soon

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Protection and PoisonsSubstrates, superstrates and seals vary by application and production§ Substrates may be fabricated

or purchased§ Superstrates may be fab’d or

laminated§ Seals may be formed or

dispensed (adhesives)Chemical, mechanical and optical factors vary by device and by application

David Barnes 1/8/14 6

SubstrateDevice

SuperstrateSealSeal

O2

H2ODelamin-

ation

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Operation and Performance Effects

Effect Emitter Side Back Side

Chemical Permeation rateInteraction with device

Permeation rateContamination (migration)

Mechanical Thermal excursion, CTELayer adhesion, strain

Adhesion, seal integrityExpansion/contractionStrain, delamination, etc.

OpticalRefraction, diffusion, etc.Reflection, UV protectionTransmission, extraction

Reflection or cancellationScratch, dirt resistanceCosmetics, etc.

David Barnes 1/8/14 7

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Fabrication or Lamination Effects

David Barnes 1/8/14 8

Sup

erst

rate

Sub

stra

te

Topemitter

Bottomemitter Deposition—Adhesion

Migration—Interaction

Work Function—MorphologyDeposition—Separation—Strain

Refraction—Diffusion—AbsorptionEmission—Migration—Interaction

Work Function—MorphologyDeposit/Remove—Optics, etc.

Condition—ContaminationAdhesion—Morphology

Condition—AdhesionRefraction—Diffusion, etc.

Refraction—Diffusion—AbsorptionAdhesion—Emission—Migration

Fabricated Laminated

Condition—ContaminationAdhesion—Interaction

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Formation—Deformation (bendy) Effects

Effect Formation Deformation (bendy)

FabricatedThermal excursion, distortionSheet: deposit, releaseWeb: stretching, scoring…

Thermal mismatching, strainCracking or shifting insideReflection (gap) changes

LaminatedContamination, strainSheet: adhesion, flatnessWeb: wavy edge seal

DelaminationCracking or shifting inside (e.g. nanoparticles in matrix)

Operation Haze formation, UV effectsOcclusions, particles

LifetimeBending radius

David Barnes 1/8/14 9

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Evolution of Barrier TechnologiesMany materials and methods used today started in the 1970’s as means for protecting thin-film capacitors

IP claims and counterclaims are possible, once there is a market to argue over… for now, inventions are becoming more specific

Evolution can be evaluated on three axes§ Better films—materials and methods§ Composite films—multiple layers, cross-links§ Reactive films—scavengers, hydrophobics

1/8/14David Barnes 10

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Basic ConceptsSolid or glassy metal foils make great, but opaque barriersTransparent barriers made of metallic oxides (e.g. sapphire) would be great if they had no holes or cracks… and if they didn’t get damaged so easilySo engineers make the best oxide “barrier layer” they can for a given cost, then protect it with a polymer coating

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Protective PolymerOxide, Nitride, Carbide…

(Substrate)

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Better Barrier Film Layers

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Goal PVD (sputter) CVD ALDFilm density Medium High High

Defect density GoodTime dependent

Better, no PVD bombardment Best

Stoichiometry Fixed by target Variable by precursor mix

Variable by precursor mix

Speed (rate) Fast Slower Slowest

Cost Best Good Challenged

Example SDI or Vitriflex UDC Beneq

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Composite FilmsThe NREL-Vitex multi-layer way to minimize effect of pin-holes continues with SDI efforts todayN-O-N R&D at the Holst Centre continues Philips approach

Cross-linked SiO-N (silazane) by Konica Minolta combined with SiO (siloxane) under UV cureNano-composite experiments with clay-like materials are still ongoing as a coated method

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PolymerOxide, Nitride, Carbide…

(Substrate)

PolymerOxide, Nitride, Carbide…

Polymer

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Reactive (Scavenger) FilmsReactive films or particles in a matrix can delay permeation and hydrophobic surfaces can repel water, c.f.§ Tera-Barrier Films WO2013062486§ Vitriflex PCT/US2012/022809

CNT and other nanoparticles are of interest here with some graphene research, also§ Tera-Barrier Films US2012016443

§ Survey DOI:10.1002/app.39628

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CaO, ZTO, CNT…Oxide, Nitride, Carbide…

(Substrate)

Polymer

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Advances in Barrier TechnologiesThe goal remains a permeation rate that matches product lifetime within an acceptable range of capital and operating costs

The central problem remains balancing film (barrier) quality with productivity for a wide range of mechanical and optical systems

The challenge remains one of developing a specific material-tool system without benefit of industry consensus or scale

Key areas of product development§ Thin Film Encapsulation (TFE)—SDC and new tools§ TFE Alternatives—LGD plus Dam & Fill§ Laminates—3M, Konica Minolta, Vitriflex, et alii

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-

1

2

3

4

5

6

7

8

9

5 15 25 35 45 55 65 75 85 95

50 ppi

100 ppi

200 ppi

400 ppi

Reviewing the Goal: Risk ReductionGiven a defect can be as small as 50 nm, and product lifetimes can range from 18–180 months, we can see risks for large panels as high as risks for small panels*Thus, barrier levels are important for both large and small panel makers considering OLEDScaling methods up to TV panel sizes is a major challenge

*Arbitrary units scaled relative to 50 ppi at 5” HD diagonal

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50 nm Defect Sensitivityversus

Diagonal Inch (HD)

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Risk: Diffusion and Permeability of a SoluteThe pace of diffusion through a thin film is linear if the solubility is the similar inside the film.In this simple case, the time for a solute (e.g. water) to move through the barrier film depends on the thickness of the film.The concentration gradient between inside and outside depends on the solute, the film and temperature (energy)…It is called permeability.

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C1

C0

Film

AbsorptionDiffusion

Desorption

Con

cent

ratio

n

Thickness or length

inside

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Thin Film Encapsulation, e.g. SDC

TFE Upside Downside

Application Proprietary tuning of film for optics, etc

Complex interactions;Immature supply base

Position Early stage production Cost challenge

WVTR* (10-x) E-6+ E-5 (fewer dyads)

Materials Polyacylate on AlO Cost per dyad

Processes PVD (SNU…) & Coating Throughput, quality

Alternates, Variations Kateeva, Veeco Universal Display

Futures Flexible mobile displays TV panel cost-price

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*Nominal water-vapor transmission rate, indicative only

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Laminates, e.g. Konica Minolta

TFE Upside Downside

Application Scalable x-linking of coated polymers

Less differentiated in optical attributes

Position Production Si-O-N + NH

WVTR* (10-x) E-5+ E-4+

Materials Siloxane, Silazane Cost

Processes Coat and VUV Drying, purging

Alternates, Variations Mitsubishi 3M, LG Chem

Futures Flex substrates Market development

David Barnes 1/8/14 19

*Nominal water-vapor transmission rate, indicative only

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Laminates, e.g. Vitriflex

TFE Upside Downside

Application Cost-effective laminateusing scavenger layer

Unproven sealing methods

Position Pilot line production More PV than OLED

WVTR* (10-x) E-6? E-5+

Materials ZTO, CaO, acrylates… Reactive delay time?

Processes PVD and coat Need for ALD?

Alternates, Variations Tera-Barrier Films Beneq (ALD)

Futures Flex substrates PV market dynamics

David Barnes 1/8/14 20

*Nominal water-vapor transmission rate, indicative only

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Readings and ResourcesPermeation and ReliabilityKempe—http://www.nrel.gov/pv/performance_reliability/research_staff.html#Kempehttp://www.nrel.gov/pv/performance_reliability/publications.html

Graff, Weaver et al—doi:10.1117/12.416878

Weaver—https://www.rti.org/pubs/ThinFilm_Flexible_OLEDS.pdf

Stanislav—doi:10.1080/00914030390224337

Colye—doi:10.1002/pip.1172Park—http://iopscience.iop.org/0268-1242/26/3/034001

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Tools and MaterialsALD—http://dx.doi.org/10.1063/1.4757907CVD—https://www.google.com/patents/US8592253iCVD—http://onlinelibrary.wiley.com/doi/10.1002/adfm.200701479/abstractGraphene—http://onlinelibrary.wiley.com/doi/10.1002/app.39628/abstractCeramics—http://onlinelibrary.wiley.com/doi/10.1002/j.2168-0159.2013.tb06219.x/abstractDavid Barnes, BizWitz— [email protected]