1 of 22

By: Claire Floyd, Ethan Golovach, Noah Greene, Thomas Headley, and Thomas Brunner

Changing technology today

2 of 22

Overview

Mechanical Structure
Current Design of OLED
Processing
Mechanical Properties
Imperfections
Thermal Properties
Types of OLED
Applications
Advantages vs. Disadvantages
Current Research

3 of 22

Material Structure

Main structure

Light emitting layers
Seven ring state for glass like structure
Azulenes for light emissions

“Color Filter Method”
Common: yellow and blue (color filters)

Empirical formula: C₃₆H₂₄N₂
Molecular weight: 484.59 g/mol
Crystal structure

photonic crystal structure
Study mentioned: metallic-dielectric photonic structure

OLED’s are made of a series of this, light emitting films. These structure hold a seven ring state to hold a glassy like structure, however, at different temperatures it will be at a liquid state.

The helical structure of azulenes as seen in the red can be seen in the crystal structure. Azulenes have light absorption properties and will produce a green yellow color which causes the light emitting layer (as seen above). But, different colors can be created through something called a “Color Filter Method” where the bonds are created to produce a specific color and the white light behind the bond allows the light to be absorbed and emits the visible color. The most common colors are yellow and blue otherwise color filters are used to change the colors.

These molecules are given by the following CH chains with Nitrogen as well creating this empirical formula. These chains create a Network when it is solidified and will create a photonic band when the heat is applied. In the example above they are in a hexagonal phase which can be in 3 and 4 fold CH chains with tetragonal and rhombohedral symmetry.��One of these crystals has a molecular weight of 484.59 g/mol.

In regards to the crystal structure, the vertical stacking of the microcavity (surface emitting semiconductor, light confined by cells, and a dielectric mirror to close the cavity) produce an alternating metal-dielectric photonic crystal structure. All of the structures are photonic crystals in which the wave lengths and reflections cause color to be produced. This band structure allows more energy to travel through the unit cells. Respectively in the figure above, it shows that with the increase in metal that it decreases the bandwidth creating an internal electric field that will emit a specific color. In the example above they used metallic layers to measure the colors where the 6 stacked microcavities the colors would be more apparent and cause a larger contrast.

4 of 22

Layer Breakdown in a OLED

Cathode: negatively charged to inject electrons
Electron Transport Layer
Blocking Layer: confines electrons to the emissive layer
Emissive Layer: energy is converted to light or photons

(crystal structure is present)

Hole Transport Layer
Hole injection Layer: allows a decrease in energy refractions and energy to travel throughout the entire area
Anode: may be transparent, positively charged
Substrate: foundation (glass,etc)

5 of 22

Current design of OLED material

Planar stacking advantages

Blurring
Diffraction
Vulnerability to Electrical shortages

Solid-state device : a thin, carbon-based semiconductor that emits light when electricity is applied by adjacent electrodes
Current Market

Apple product advancements
No polarizing layer to emit light and create a brighter image

How to measure efficiency

Number of photons that reach the surface area of the screen

In the previous slide, we went over what each layer does on an atomic level, but what about on a visual level. This structure looks like from the nacked eye that of planar stacking. The planar stacking allows the light to be free of side effects such a blurring, diffraction, and vulnerability to electrical shortages.

This planar stacking builds a solid-state device consisting of a thin, carbon based semiconductor that emits light when electricity is applied by adjacent electrodes. Essentially, electrons have the ability to travel through the holes in the final layers of the OLED. The waves of these electrons allow color to appear depending through the amount of light that is controlled by the amount of electricity that is allowed to flow through.

This current design is mostly seen in the foldable touch screen cell phones that we currently see on the market, but apple is trying to produce a similar product for enhanced screen capabilities. The screen will no longer have to use a polarizing layer to emit light and it will create a brighter image.

In particular, because apple wants to change to non-polarizing screens, they may use stacking that is similar to the Stacked OLED in later models to have the brightest images, even though yes this is for white light, it may look similar to this structure.

In current research they are looking at how to increase the efficiency by outcoupling photons which is the increasing the number of photons that reach the surface area of the screen.

6 of 22

Processing of OLED’s

More layers can be added, but basic process is as follows
Anodes are applied to a substrate material

Plastic
Glass

Organic, conductive molecules are applied to the anode

Typically via inkjet processing

An emissive layer is then added using a similar process

Basic structure:

7 of 22

Processing Cont.

A cathode is then placed on the opposite end of the anode
All layers are then encased – This is the “seal”

Plastic
glass

Current flows from cathode to anode, passing through all layers
Light is emitted as a result

8 of 22

Mechanical Properties

OLED is made from Organic Materials
Quantum Yield:�‘ratio of the photons emitted by the photons absorbed’

OLED materials show “intense photoluminescence with near unity quantum yield”

High Fluorescence Efficiency: (creates color)�“fast decay of excited molecular states”
Electron Mobility Range: 10^-8to 10^-2 cm²/(V*s)

9 of 22

Mechanical Properties

In OLED, the mechanical durability is mainly dependant on the substrate rather than its components
(PES) Polyethersulfone - �Common substrate used around OLED

Young's Modulus - 2.6 GPa
Flexural Strength - 130 GPa
Tensile Strength - 87 MPa

10 of 22

Imperfections

Exposure to air after fabrication leads to contaminant pollution
Imperfections in the morphology of the anode surface determine the quality of organic/electrode interface
Interface quality has a direct correlation to electrical shorts and the following degradation
Particle contamination incorporated during device fabrication is often associated with “spikes”
“Spikes” are a phenomenon of local heating and subsequent electrical break-through

11 of 22

Thermal Properties

Thermal management is important for the efficient operation of organic light-emitting diodes
Elevated temperatures will accelerate device degradation, influencing both lifetime and performance
The temperature increase in a current driven organic device occurs via internal Joule ‘‘self-heating’

12 of 22

13 of 22

AMOLED vs PMOLED

The term AMOLED means Active-Matrix OLED. The 'active-matrix' part refers to the driving electronics, or the thin film transistor (TFT) layer.

This TFT layer contains a storage capacitor that maintains the line pixel states, and so enables large size (and large resolution) displays.

14 of 22

AMOLED vs PMOLED

A PMOLED uses a simpler kind of driver electronics - without a storage capacitor. This means that each line is turned off when you move to the next line.
More voltage is used which shortens the lifetime of the OLED materials and also results in a less efficient display.
So while PMOLEDs are cheaper to make than AMOLEDs they are limited in size and resolution (the largest PMOLED is only 5", and most of them are around 1" to 3"). Most PMOLEDs are used for character display, and not to show photos or videos.

15 of 22

Applications

Any technology with a screen is a candidate to be manufactured with OLED

i.e. iPhones, TV’s

Wearable technologies

Ex. Smart watches, fitness bands

Foldable screen devices
Virtual Reality (VR) headsets

16 of 22

Advantages and Disadvantages

Advantages:

They are emmissive by nature – resulting in brighter colors compared to LED

Less power required

The viewing angle is larger than LED’s, which results in higher resolution and clearer picture
Extremely flexible - can be used for flat and foldable applications
Green technology - Uses no toxic materials

Disadvantages:

Highly susceptible to water damage
The lifespan is shorter when compared to LED – this leads to higher production costs
Visibility under sunlight is poor
Currently very expensive to use in manufacturing

17 of 22

18 of 22

Current research developments: Flexibility of OLED’s

OLED’s are highly stable under high stress and ductility
New Design

OLED’s into plastic substrates
E.g. cloth like material
Constituent layers of OLED’s
Dipping into a solution based PLED fibers

Further studies need to be done to measure safety of this composite

Safety vests

Dr. Lee and their team have come up with a way to make the most reliable and flexible OLED’s by placing them on plastic substrates. OLED’s, however, need metal electrodes produce highly stable performance when they experience tensile stresses due to ductility. When electrons flow through the metal films and cause the temperature to be heated, it will become more ductile, but placing them in flexible material, it will enhance light extraction efficiency because it now has a tensile stress.

In this project, they looked at the lowest hybrid structure (metal and plastic substrate) material that could potentially diminish encapsulation thickness without deterioration. Here they looked at different fibers where they can place OLED’s in different wearable applications, but reliability still needs to be ensured before they are commercialized and put on the market.

In the image to the right, Dr. Lee’s lab was working on putting these OLEDs in cloth like material. They looked at deposit constituent layers of OLEDs and dipping it into a solution based PLED fibers. PEDOT:PSS solution is a film that allows electrical conductivity. SY bath just encapsulates the previous bath. As stated before, further studies need to be completed to determine safety and other conditions before it is placed in clothing. But, this opens the way to the future of design of clothing and safety as well.

An example includes: safety vests no longer needing light to reflect off of them to produce light

19 of 22

Contributions

Material Structure Slides: Claire Floyd (Slides 3-4)

Current Design: Claire Floyd (Slide 5)

Processing: Claire Floyd, Noah Greene (Slides 6-7)

Mechanical Properties: Noah Greene, Thomas Headley (Slides 8-9)

Imperfections: Thomas Brunner (Slide 10)

Thermal Properties: Thomas Brunner (Slide 11)

Types of OLED: Ethan Golovach (Slides 12-14)

Applications: Ethan Golovach, Noah Greene, Claire Floyd (Slide 15)

Advantages and Disadvantages: Noah Greene, Ethan Golovach (Slide 16)

Research developments: Claire Floyd (Slide 18)

20 of 22

Works Cited

Allemeier, David, et al. “Emergence and Control of Photonic Band Structure in Stacked OLED Microcavities.” Nature News, Nature Publishing Group, 20 Oct. 2021, https://www.nature.com/articles/s41467-021-26440-3.

“CBP Molecule: OLED Host Material, 58328-31-7.” Ossila, https://www.ossila.com/en-us/products/cbp.

Europe, eeNews. “OLED Outcoupling Layer Is Wavelength and Viewing-Angle Independent.” EENewsEurope, 17 July 2018, https://www.eenewseurope.com/en/oled-outcoupling-layer-is-wavelength-and-viewing-angle-independent/.

“OLED Basics.” Energy.gov, https://www.energy.gov/eere/ssl/oled-basics.

Chen, Hung. “Recent progress of molecular organic electroluminescent materials and devices.” Materials Science and Engineering: R: Reports, 1 Dec. 2002, https://www.sciencedirect.com/science/article/pii/S0927796X02000931?ref=cra_js_challenge&fr=RR-1.

“Organic Light Emitting Diodes (Oleds).” Universal Display Corporation, 3 Jan. 2017, https://oled.com/oleds/.

“A Review of Flexible Oleds toward Highly Durable Unusual Displays.” IEEE Xplore, https://ieeexplore.ieee.org/abstract/document/7827119.

Szlachcic, Paweł, et al. “Organic Light Emitting Diodes (OLED) Based on Helical Structures Containing 7-Membered Fused Rings.” Dyes and Pigments, Elsevier, 7 Nov. 2014, https://www.sciencedirect.com/science/article/pii/S0143720814004185.

21 of 22

Works Cited

“Technologies: OLED Display: Soar Corporation (the Former ‘Yonezawa Plant’ of Tohoku Pioneer Corporation) - Ofifcial Website.” Technologies | OLED Display |SOAR CORPORATION (the Former "Yonezawa Plant" of Tohoku Pioneer Corporation) - Ofifcial Website, https://www.soar-tech.co.jp/en/oled/introduction/.

“AMOLED - Introduction and Market Status.” OLED, 19 Oct. 2021, https://www.oled-info.com/amoled.

“Impact of Temperature on the Efficiency of Organic Light Emitting Diodes.” Organic Electronics, North-Holland, 24 July 2015, https://reader.elsevier.com/reader/sd/pii/S1566119915300549?token=1E24B806D3B8D1CEB6C5BE735CDDEDE9448824EE16A74A5CA8AA9E58AFC7119525E18A844E1D5088ACF763CCD6DC65A8&originRegion=us-east-1&originCreation=20221114205036.

“Degradation of Organic Light-Emitting Diodes under Different Environment at High Drive Conditions.” Organic Electronics, North-Holland, 7 Nov. 2006, https://reader.elsevier.com/reader/sd/pii/S1566119906001455?token=DC6D93D311E5EF6716CC5FB4AD587E2A8E4CABAF7F4F0FF301F858E8B37E3E74DB5E6108D9D5FE9A1094CF77CB6F2C63&originRegion=us-east-1&originCreation=20221114190520.

Thermal Properties of Organic Light-Emitting Diodes. http://www.math.lsa.umich.edu/~krasny/paper_org_elec_2012.pdf.

“Manufacturing Process of OLED: ABOUT OLED: Products and Services.” Canon Tokki Corporation, https://tokki.canon/eng/business/el/process.html.

Michiganengineering, director. YouTube, YouTube, 1 Feb. 2017, https://www.youtube.com/watch?v=g3YAZZ486qk. Accessed 14 Nov. 2022.

“Thermoplastic.” MakeItFrom.com, 30 May 2020, https://www.makeitfrom.com/material-properties/Polyethersulfone-PES/.

22 of 22

Questions?