Polarization-Controlled Two-Dimensional White-Light Spectroscopy of Semiconducting Carbon Nanotube Thin Films

TitlePolarization-Controlled Two-Dimensional White-Light Spectroscopy of Semiconducting Carbon Nanotube Thin Films
Publication TypeJournal Article
Year of Publication2016
AuthorsMehlenbacher RD, McDonough TJ, Kearns NM, Shea MJ, Joo Y, Gopalan P, Arnold MS, Zanni M T.
Secondary TitleThe Journal of Physical Chemistry C
Date Published06/2016
PublisherJournal of Physical Chemistry C

Polarized two-dimensional white-light (2D-WL) spectra are reported for thin films of semiconducting carbon nanotubes. The orientational responses for 4-point correlation functions are derived for samples that are isotropic in two dimensions. Spectra measured using ⟨−45°,+45°,0°,90°⟩ polarizations eliminate the diagonal peaks in the spectra arising from S1transitions to uncover cross peaks to a weaker transition that is assigned to radial breathing modes. In nanotubes purified by unwrapping PFO-BPY polymer using metal chelation, an absorption at 1160 nm is observed that is assigned to hole doping that forms trions. The trion peak may have a transition dipole nonparallel to the S1 transitions, and so its cross peak is prominent in polarized 2D-WL spectra. Energy transfer of photoexcitons to the trion peak occurs within 1 ps. Identifying and understanding the effects of purification on the electronic structure of thin films of semiconducting carbon nanotubes is important for learning how the inherent photophysics of individual carbon nanotubes translates to coupled nanotube thin-film materials.