Carrier Lifetime Enhancement in a Tellurium Nanowire/PEDOT:PSS Nanocomposite by Sulfur Passivation

TL;DR

This study investigates how sulfur passivation affects carrier lifetime and conductivity in tellurium nanowire/PEDOT:PSS nanocomposites, revealing that sulfur treatment extends carrier lifetime despite reducing overall conductivity.

Contribution

It demonstrates that sulfur passivation increases carrier lifetime and modifies surface recombination velocities in tellurium nanowire composites, providing insights for thermoelectric material optimization.

Findings

Sulfur passivation extends carrier lifetime.

Surface recombination velocities vary with passivation.

Real terahertz conductivities are much higher than DC conductivities.

Abstract

We report static and time-resolved terahertz (THz) conductivity measurements of a high- performance thermoelectric material containing tellurium nanowires in a PEDOT:PSS matrix. Composites were made with and without sulfur passivation of the nanowires surfaces. The material with sulfur linkers (TeNW/PD-S) is less conductive but has a longer carrier lifetime than the formulation without (TeNW/PD). We find real conductivities at f = 1THz of {\sigma}(TeNW/PD) = 160 S/cm and {\sigma}(TeNW/PD-S) = 5.1 S/cm. These values are much larger than the corresponding DC conductivities, suggesting DC conductivity is limited by structural defects. The free-carrier lifetime in the nanowires is controlled by recombination and trapping at the nanowire surfaces. We find surface recombination velocities in bare tellurium nanowires (22m/s) and TeNW/PD-S (40m/s) that are comparable to evaporated tellurium thin films. The surface recombination velocity in TeNW/PD (509m/s) is much larger, indicating a higher interface trap density.