1. Nesibe Lakhani EECS 277A Prof. Richard Nelson
OLED Fabrication
Nesibe Lakhani
EECS 277A
Prof. Richard Nelson

2. OLED Structure
OLEDs are light emitting devices that have a thin film of organic compounds as its emissive electroluminescent layer.

3. Fabrication Methods Physical Vapor Deposition Screen Printing
Ink Jet Printing
In-line Fabrication

4. OLED Fabrication Steps

5. Physical Vapor Deposition (PVD)

6. 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

7. 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

8. Disadvantages of PVD Expensive Not flexible
Has no control to direct the materials to deposit on the desired areas
Inefficient use of materials

9. 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

10. Screen Printing Steps The mesh material is stretched across a frame
Hole transport layer prepared using a solution of diamine, polycarbonate, and rubrene.
Squeegee is used to wipe solution through the open mesh
Resulting film covers entire surface of ITO
Electron transport layer (ETL) and cathode are deposited by PVD

11. 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

12. 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

13. 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

14. Ink Jet Printing
Ink jet printing to define and pattern RGB emitting subpixels

15. In-Line Fabrication
Mass production technique
Vertical in-line tool operates with continuous substrate flow
Linear sources of depositing organic and metallic materials

16. In-Line Fabrication Excellent thickness homogeneity
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

17. OLED Fabrication Roadmap

18. 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.
Muhamad Mat Salleh, et.al., Fabrication of Organic Light Emitting Diodes.