Tuning counterion chemistry to reduce carrier localization in doped semiconducting carbon nanotube networks

Understanding and controlling the impact that electrostatic interactions have on the transport of injected charge carriers is important for the utilization of pi-conjugated semiconductors in opto-electronic applications. Here, we explore the impact of dopant chemical and electronic structure on the doping efficacy and charge carrier transport in semiconducting single-walled carbon nanotube (s-SWCNT) networks using molecular charge-transfer dopants based on functionalized icosahedral dodecaborane (DDB) clusters. Calculations indicate that localization of electron density on the DDB core reduces the coulombic interactions that contribute to hole localization in the s-SWCNTs, thereby improving charge carrier transport. The enhanced delocalization produces an increase in the electrical conductivity and thermopower at lower charge carrier densities, yielding enhanced thermoelectric transport and a thermoelectric power factor that surpasses the previous best in class for enriched s-SWCNT thin-film networks. This strategy can be applied broadly across pi-conjugated semiconductors to tune and enhance performance in a variety of energy harvesting devices. [Display omitted] •Molecular charge-transfer dopant with electron affinity tunable by chemical structure•Carrier-counterion interactions reduced by localization of extracted electron•Delocalization of hole improves thermoelectric charge transport•Thermoelectric power factor surpasses best for enriched carbon nanotube networks Murrey et al. demonstrate improved transport of chemically injected charge carriers in enriched semiconducting carbon nanotube networks. By employing functionalized icosahedral dodecaborane clusters as the dopant, the coulombic interactions between the hole and the associated counteranion can be reduced. This enables enhanced thermoelectric transport and power factor.