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