Charge Transport in Networks of sp3-Functionalized Single-Walled Carbon Nanotubes

Abstract

The controlled introduction of luminescent sp3 defects into semiconducting single-walled carbon nanotubes (SWCNTs) leads to narrowband, tunable emission in the near-infrared and increases their photoluminescence (PL) quantum yield for potential optoelectronic applications [ACS Nano 2019, 13, 9259]. While the spectroscopic properties of sp3-functionalized SWCNTs are already well-established, a detailed understanding of the impact of functionalization on their electrical performance especially in a network is still lacking. Here, we investigate charge transport in ambipolar, light-emitting field-effect transistors based on networks of pristine and sp3-functionalized (6,5) SWCNTs. While both hole and electron mobilities decrease with increasing degree of functionalization, the transistors remain fully operational, showing electroluminescence from the defect states. Charge-modulated PL spectroscopy, which exclusively probes the mobile charge carriers in SWCNT networks [ACS Nano 2020, 14, 2412], confirms that the defects are efficiently sampled by mobile carriers and consequently, sp3-functionalized SWCNTs actively participate in the charge transport within the network. Temperature-dependent transport measurements of transistors combined with ultrafast photoconductivity dynamics of individually dispersed SWCNTs measured by optical-pump THz-probe spectroscopy provide further insights into the impact of sp3-functionalization on charge transport within a single nanotube and within a network.