Center on Materials & Devices for Information Technology ResearchAn NSF Science & Technology Center
July 20th, 2006
Investigating Carbon Nanotube Films for Potential Electrode
Applications
Patrick Duggan, MDITR REU student
Center on Materials & Devices for Information Technology ResearchAn NSF Science & Technology Center
July 20th, 2006
Outline• Motivation for creating
electrodes from CNT
• Creating thin films of CNT– Procedure– Problems
• Modes for improvement– Production– Augmentation of Sampling
• Results and Recommendations
OLED Device
Center on Materials & Devices for Information Technology ResearchAn NSF Science & Technology Center
July 20th, 2006
Problems with Entrenched Technology
Brittle material tensile failure (crack) strain
ITO (Indium-tin oxide) 2.5%
ITO (evaporated on PET) 1.2% ~ 2.0% depends on thickness
thin film• ITO (Indium Tin Oxide) currently used for electrodes
– Highly conductive– Highly transparent in visible spectrum
• ITO is brittle making it inflexible
• Mechanical limitations of brittle materials – tensile/compressive stresses in the barrier layers– shear stress between layers– adhesion strength between thin film layers
(Crawford, G., Cairns, D., (Nov. 2005). Flexible Substrate )
Center on Materials & Devices for Information Technology ResearchAn NSF Science & Technology Center
July 20th, 2006
Why create thin films of CNT?
• CNT remain conductive under stress– Same amount of contact points
• Creation of Flexible Electronics– Flexible OLEDs and OPVs
• GOAL: CNT films w/comparable– Conductivity– Transmittance
Center on Materials & Devices for Information Technology ResearchAn NSF Science & Technology Center
July 20th, 2006
Creating thin films of CNT
The Solution Vacuum Filtration
Membrane RemovalAttaching Substrate
CNT Deposition
Final Product
Center on Materials & Devices for Information Technology ResearchAn NSF Science & Technology Center
July 20th, 2006
Problems in creating the CNT films
Creases
Cracks Air Bubbles
Radial Defects
Tears
Conglomerates
Center on Materials & Devices for Information Technology ResearchAn NSF Science & Technology Center
July 20th, 2006
Improving the Procedure
• Dilution– Where does dilution happen?– Improvement from DI water– Results
• Dispersion Solution– DMF (dimethyl formamide)– Nitromethane– Results
SWCNT:DMF solution
1.E+03
1.E+04
1.E+05
0.01 0.1 1
Nanotube amount (mg)
Sh
ee
t R
es
ista
nc
e (
Ω/s
q.)
on PET
diluted in DI water
diluted in DMF
Center on Materials & Devices for Information Technology ResearchAn NSF Science & Technology Center
July 20th, 2006
Augmentation of Sampling
• Heat– Evaporate remnants of chemicals– Results
• Silver– 3-5 nm layer– Solder CNT network– Results
• Additional attempts– PEDOT:PSS – Light, high efficiency
Center on Materials & Devices for Information Technology ResearchAn NSF Science & Technology Center
July 20th, 2006
Comparison to ITO
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
0 500 1000 1500 2000 2500 3000
Sheet Resistance (Ω/sq.)
Tra
nsm
itta
nce
at
550
nm
PET w/heat
w/silver
*Nitromethane
*Nitromethane w/silver
ITO
Center on Materials & Devices for Information Technology ResearchAn NSF Science & Technology Center
July 20th, 2006
Recommendations
• Significant progress made from Nitromethane– Test other solvents
• Alignment of CNT network, Composite films, Multiple baths
• More research will create a comparable electrode to ITO
• Potential use in Top Emitting OLEDs
• Potential use in infrared regime
Center on Materials & Devices for Information Technology ResearchAn NSF Science & Technology Center
July 20th, 2006
Acknowledgements
• Dr. Samuel Graham, faculty advisor• Roderick Jackson, student advisor• Nam Su Kim, mentor• Entire research group• William Potscavage and Kippelen Group• Olanda Bryant and Dr. Keith Oden, program
directors