Charge Modulation Spectroscopy of Pristine and sp3-Functionalized Single-Walled Carbon Nanotube Networks

Abstract

The controlled decoration of single-walled carbon nanotubes (SWCNTs) with luminescent sp3 defects has emerged as a powerful approach to enhance their usually low photoluminescence (PL) quantum yields and achieve tuneable emission across the near-infrared even for polymer-wrapped nanotubes [ACS Nano 2019, 13, 9259]. However, their application in optoelectronic devices requires a detailed understanding of the impact of sp3 functionalization on their electrical performance. While isolated sp3 defects on single SWCNTs increase the resistance by a few kΩ, the effect of functionalization on charge transport in networks of semiconducting SWCNTs remains unexplored. Charge modulation spectroscopy is ideally suited to probe the mobile charge carriers in SWCNT networks and has previously corroborated the notion that charge accumulation and transport in mixed SWCNT networks is highly chirality- and gate voltage-dependent. Here, we use charge-modulated PL (CMPL) spectroscopy to study the current pathways in field-effect transistors based on networks of pristine and functionalized (6,5) SWCNTs. We find that the defects are very efficiently sampled by mobile carriers and consequently, sp3-functionalized SWCNTs actively participate in the charge transport in these networks. In combination with voltage-dependent PL and electroluminescence measurements, our CMPL method provides fundamental insights into the interaction of charge carriers with sp3 defects in SWCNT thin film devices.Fig. 1: Schematic of the charge modulation PL spectroscopy setup (left) and CMPL spectra of pristine and functionalized (6,5) SWCNT network field-effect transistors (right). Figure 1