Charge and Thermoelectric Transport in Polymer-Sorted Semiconducting Single-Walled Carbon Nanotube Networks*

We report charge density and temperature-dependent field-effect mobility and on-chip gated Seebeck coeff. measurements¹ of polymer-sorted monochiral small diameter (6,5) (0.76 nm) and mixed large diameter SWCNT (1.17-1.55 nm, plasma torch, RN) networks with varied network densities and length distributions. We show that charge and thermoelectric transport in SWCNT networks can be modelled by the Boltzmann transport formalism, incorporating transport in heterogeneous media and fluctuation-induced tunneling. Considering the diameter-dep. 1D density of states (DoS) of the SWCNTs, we can simulate the Seebeck coeff.. Our simulations suggest that scattering in these networks cannot be described as 1D phonon scattering. The relaxation time is instead inversely prop. to energy, presumably pointing towards the necessity to include scattering at SWCNT junctions and the more 2D character of scattering. Observing higher power factors in trap-free, ttmgb-treated (6,5) than in the RN networks, emphasizes the importance of chirality selection to tune the width of the DoS. Hence, we propose trap-free, narrow DoS distr., large diameter SWCNT networks for electronic and thermoelectric applications.²
[1] Statz et al. Commun. Phys. 1, 16 (2018)
[2] Statz et al. ACS Nano (in review, 2020)