| AVS 55th International Symposium & Exhibition | |
| Nanometer-scale Science and Technology | Wednesday Sessions |
| Session NS+NC-WeA |
| Session: | Nanoscale Devices and Sensors |
| Presenter: | T.M. Barnes, National Renewable Energy Laboratory |
| Authors: | T.M. Barnes, National Renewable Energy Laboratory J.L. Blackburn, National Renewable Energy Laboratory R.C. Tenent, National Renewable Energy Laboratory M.J. Heben, National Renewable Energy Laboratory T.J. Coutts, National Renewable Energy Laboratory |
| Correspondent: | Click to Email |
Single-wall carbon nanotube (SWCNT) networks exhibit high electrical conductivity and optical transparency, allowing their use as transparent electrical contacts in photovoltaics and other opto-electronic devices. They are particularly well suited to applications requiring a contact that is flexible, hole-conducting, or solution processible. We have shown in previous work that these materials function well as transparent contacts in a variety of organic and inorganic photovoltaic devices. However, their opto-electronic performance still lags that of the best transparent conducting oxides. Improving charge transport through the networks should enable higher conductivity and the use of thinner (and more transparent) networks. In this work, we focus on the conductivity mechanisms of transparent SWCNT networks as a function of the ratio of metallic to semiconducting tubes and chemical doping. Conductivity in SWCNT networks is influenced by a variety of factors. Junctions between the semiconducting and metallic tubes are thought to strongly affect network conductivity, but this is not well understood. Following the method of Arnold,1 we have produced films that contain a range of tube conductivity types varying from strongly semiconductor enriched (96%) to strongly enriched in metallic tubes (96%) to study the effect of tube-type polydispersity on transport. Temperature dependant resistivity measurements are combined with spectrophotometry to characterize the networks revealing that both intentional and unintentional doping has a strong effect on network conductivity, regardless of tube-type. Tube-type and tube quality do appear to affect the high temperature stability of the conductivity. We present a model effectively describing the conductivity mechanism at low temperature and explore the factors controlling conductivity at higher temperatures.
1 Arnold, M. S.; Green, A. A.; Hulvat, J. F.; Stupp, S. I.; Hersam, M. C., Sorting carbon nanotubes by electronic structure using density differentiation. Nature Nanotechnology 2006, 1, 60-65.