Harvesting Energy with Semiconducting Single-walled Carbon NanotubesJeff Blackburn

National Renewable Energy LaboratoryContact e-mail: jeffrey.blackburn@nrel.gov

Semiconducting single-walled carbon nanotubes (s-SWCNTs) are unique organic semiconductors with diameter-tunable band gaps, high absorption coefficients in the near-infrared and visible, and extremely high charge carrier mobility. These qualities motivate fundamental and applied studies on the use of s-SWCNTs in energy harvesting schemes, either through direct energy harvesting in the s-SWCNTs themselves or across interfaces with organic, inorganic, or hybrid absorber layers. As an example, s-SWCNTs can be incorporated as an active absorbing layer or as charge extraction layers in solar cells. 1

Alternatively, broad ranges of thermal energy (e.g. waste heat) can be harvested in SWCNT thermoelectric (TE) materials.2 In this talk, I will discuss our fundamental opto-electronic studies of thin s-SWCNT films with highly tunable electronic properties. A unifying theme in this research is the development of tools and strategies for spectroscopically tracking charge carriers, electrons and holes, in both the ground and excited states of highly enriched s-SWCNT thin films. In systems designed for photovoltaics, such strategies enable us to track critical excited-state processes that happen on femtosecond to microsecond time scales, such as exciton or charge carrier diffusion, exciton dissociation into separated charges, and charge carrier recombination.3,4 In systems designed for thermoelectric energy harvesting, such strategies enable us to sensitively tune the Fermi energy, via control of the ground-state electron or hole chemical potentials, to realize thermoelectric power factors that rival the highest performing polymer-based TE materials.5,6 These studies utilize s-SWCNTs as informative model systems for energy transduction in quantum-confined excitonic systems and also provide insights into strategies for developing efficient thin-film energy harvesting systems based on disordered nanoscale materials.

(1) Blackburn, J. L. ACS Energy Letters 2017, 2, 1598-1613.(2) Blackburn, J. L.et al. Advanced Materials 2018, 30, 1704386.(3) Ihly, R.et al. Energy & Environmental Science 2016, 9, 1439-1449.(4) Ihly, R.et al. Nature Chemistry 2016, 8, 603-609.(5) Avery, A. D.et al. Nature Energy 2016, 1, 16033.(6) MacLeod, B. A.et al. Energy & Environmental Science 2017, 10, 2168-2179.

Bio-sketch: Jeff Blackburn is currently a senior scientist and group manager of the Materials Physics Group at the National Renewable Energy Laboratory. He received his BS degree in chemistry from Wake Forest University and his Ph.D in analytical chemistry from the University of Colorado, Boulder. His work focuses on low-dimensional materials and includes the synthesis, purification, separation, and characterization of single-walled carbon nanotubes, graphene, and transition metal dichalcogenides. His research interests include exciton and charge carrier transport in low-dimensional materials, photoinduced interfacial electron transfer, solar energy harvesting, and thermoelectric energy conversion.