FIP Special Seminar - Student Speaker Award: Dynamics of charged excitons in electronically and morphologically homogeneous single-walled carbon nanotubes

The creation and decay of quasiparticles, such as excitons, polarons, and trions, in semiconductors profoundly determine the performance of modern optoelectronic devices. Unlike the widely investigated exciton and polaron, the trion, a three-body charge-exciton bound state, remains much less familiar due to its small binding energy in conventional inorganic semiconductors. Here, employing ultrafast spectroscopy and rigorously controlled charge-doping levels, we characterize trion creation and decay in single-walled carbon nanotubes (SWNTs), wherein trions are stable at room temperature. We show that SWNT trion quasiparticles exclusively derive from a precursor exciton state. More importantly, our studies demonstrate that exciton-to-trion conversion can approach unity under appropriate excitation and charge-doping conditions in carbon nanotubes. Because trions simultaneously carry excitation energy, charge and spin, the findings here may guide design of new SWNT-based optoelectronic devices that include photovoltaics, photodetectors, and spintronics. usong received his B.S. degree in School of Chemistry and Environment in Beijing University of Aeronautics and Astronautics in 2011, following which he joined Duke Chemistry and works under the advisement of Dr. Michael J. Therien. He has previously been awarded Undergraduate Distinction Award (Duke), GPNANO Fellowship, Paul M. Gross Fellowship, Burroughs Wellcome Fellowship, and the John T. Chambers Scholar from FIP.