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OLED FabricationNesibe Lakhani
EECS 277AProf. Richard Nelson
OLED Structure
• OLEDs are light emitting devices that have a thin film of organic compounds as its emissive electroluminescent layer.
Fabrication Methods
Physical Vapor Deposition Screen Printing Ink Jet Printing In-line Fabrication
OLED Fabrication Steps
Physical Vapor Deposition (PVD)
Physical Vapor Deposition
Thermal vapor evaporation of small molecules occurs in environment of 10e(-6) Torr or higher
It is usually carried out on glass substrate
Multicolor displays are made using properly matched shadow masks for depositing RGB emitting materials
Advantages of PVD
Thickness can be easily controlled 2-dimensional combinatorial arrays of
OLEDs can be easily fabricated in a single deposition procedure
PVD uses the generally available vacuum equipment that exists in the semiconductor industry
Disadvantages of PVD
Expensive Not flexible Has no control to direct the materials
to deposit on the desired areas Inefficient use of materials
Screen Printing
Used in low information content displays such as logos and signs
Thin films achieved Elements of screen printing: screen,
stencil, squeegee, ink, press bed, and substrate
Mesh materials can vary from polyester to stainless steel
Screen Printing Steps
1. The mesh material is stretched across a frame
2. Hole transport layer prepared using a solution of diamine, polycarbonate, and rubrene.
3. Squeegee is used to wipe solution through the open mesh
4. Resulting film covers entire surface of ITO5. Electron transport layer (ETL) and
cathode are deposited by PVD
Screen Printing
• For patterned hole transport layer (HTL) devices: cathode is deposited in a block larger than the HTL pattern• For non-patterned HTL: cathode is deposited through a mask to create emitting regions of known area for device output measurement
Advantages of Screen Printing
Simple Lower cost Great reduction in materials usage
because materials are only directed to the printed areas
Faster than inkjet printing More versatile
Ink Jet Printing
OLEDs are sprayed onto substrates like ink sprayed on paper during printing
Advantages: - Reduced cost- Allows OLEDs to be printed on very large
films
Ink Jet Printing
Ink jet printing to define and pattern RGB emitting subpixels
In-Line Fabrication
• Mass production technique• Vertical in-line tool operates with continuous substrate flow• Linear sources of depositing organic and metallic materials
In-Line Fabrication
• Cheaper mass production technique• Excellent thickness homogeneity• Excellent deposition stability• Complicated stack structures possible• High deposition rates/high throughput• High material usage• Large substrate handling
OLED Fabrication Roadmap
References
Ghassan E. Jabbour et al., Screen Printing for the Fabrication of Organic Light-Emitting Devices, IEEE 7:5, 2001
Joseph Shinar, Organic Light-emitting Devices. http://www.ewh.ieee.org/soc/cpmt/presentations/cpmt0401a.pdf http://www.opera2015.org/deliverables/MONA_CD-ROM/4_Symposium
%20Presentations/04-scholles2752.pdf Muhamad Mat Salleh, et.al., Fabrication of Organic Light Emitting
Diodes. http://optics.org/cws/article/research/24299