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LL8.03 - Single-Walled Carbon Nanotube Networks Fabricated by Reductive Dissolution and Their Integration into Organic Photovoltaics 
April 23, 2014   2:15pm - 2:30pm

Networks of single-walled carbon nanotubes (SWNTs) are a promising replacement for indium tin oxide (ITO) transparent electrodes due to their exceptional mechanical strength and flexibility, the great abundance of carbon, and the ability to deposit them from inks using additive, low-temperature printing processes. SWNT networks have historically had poorer conductivity-absorptivity ratios than ITO because the typical ink fabrication method, dispersing SWNTs in water with the aid of sonication, damages and shortens the nanotubes. Here, a reductive dissolution method—liquid ammonia reduction of the SWNTs to form a nanotubide salt, followed by spontaneous, sonication-free dissolution in a polar organic solvent—is employed to produce solutions of individual, unbroken SWNTs. Using these solutions we have produced transparent electrodes with significantly higher performance than those made from aqueous dispersion, which are now competitive with ITO transparent electrodes on plastic substrates. For example, SWNT films with transmittance of 89% at 550 nm wavelength and sheet resistance of 130Ω/square have been fabricated by reductive dissolution, compared to 81% transmittance and 130Ω/square for the aqueous dispersion. These SWNT transparent electrodes have been successfully integrated into organic solar cells using two different sets of active layer materials, with power conversion efficiencies reaching 3%. For thin, fast-drying active layers, SWNT-based solar cells had lower device yield and performance than ITO-based solar cells due to lower shunt resistance, while for thick, slow-drying active layers, the yield and performance of SWNT-based solar cells was very similar to that of ITO. Additionally, flexible solar cells using SWNT transparent electrodes on plastic substrates have been fabricated and show comparable performance to solar cells made on glass.

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Keynote Address
Panel Discussion - Different Approaches to Commercializing Materials Research
Business Challenges to Starting a Materials-Based Company
Fred Kavli Distinguished Lectureship in Nanoscience
Application of In-situ X-ray Absorption, Emission and Powder Diffraction Studies in Nanomaterials Research - From the Design of an In-situ Experiment to Data Analysis