Charge Transport in and Electroluminescence from sp³-Functionalized Carbon Nanotube Networks

Abstract

The controlled covalent functionalization of semiconducting single-walled carbon nanotubes (SWCNTs) with luminescent sp 3 defects leads to additional narrow and tunable photoluminescence features in the near-infrared and even enables single-photon emission at room temperature, thus strongly expanding their application potential. However, the successful integration of sp 3 -functionalized SWCNTs in optoelectronic devices with efficient defect state electroluminescence not only requires control over their emission properties but also a detailed understanding of the impact of functionalization on their electrical performance, especially in dense networks. Here, we demonstrate ambipolar, light-emitting field-effect transistors based on networks of pristine and functionalized polymer-sorted (6,5) SWCNTs. We investigate the influence of sp 3 defects on charge transport by employing electroluminescence and (chargemodulated) photoluminescence spectroscopy combined with temperature-dependent currentvoltage measurements. We find that sp 3 -functionalized SWCNTs actively participate in charge transport within the network as mobile carriers efficiently sample the sp 3 defects, which act as shallow trap states. While both hole and electron mobilities decrease with increasing degree of functionalization, the transistors remain fully operational, showing electroluminescence from the defect states that can be tuned by the defect density. KEYWORDS single-walled carbon nanotubes, covalent functionalization, sp 3 defects, electroluminescence, light-emitting field-effect transistors, charge modulation spectroscopy Supporting InformationRaman and absorption spectra of pristine and sp 3 -functionalized SWCNT dispersions, AFM image of a pristine SWCNT network, additional electrical characterization (transfer and output curves, linear mobilities, frequency-dependent capacitance) of pristine and sp 3 -functionalized SWCNT network FETs, EL spectra, voltage-and power-dependent PL spectra, estimation of excitation densities in EL and PL measurements, schematic setup for CMPL spectroscopy, additional voltage-and frequency-dependent CMPL spectra, calculation of trap densities from subthreshold swings, schematic device layout and details for gated four-point probe measurements, temperaturedependent carrier mobilities. PDF

Probing Carrier Dynamics in sp3-Functionalized Single-Walled Carbon Nanotubes with Time-Resolved Terahertz Spectroscopy

“…Note that the current hysteresis resulted from incomplete removal of oxygen and water, which act as charge traps, 39 due to the relatively low annealing temperatures that were required to avoid defect cleavage. 20 …”

“… 19 Nevertheless, recent studies have shown that the introduction of sp 3 defects also lowers the overall charge carrier mobility in dense nanotube networks. 20 The apparent convolution of intra- and internanotube transport in a network (see Figure 1 a) further complicates the interpretation of the impact of sp 3 defects. Consequently, experimental techniques are required that can determine local charge transport and carrier mobilities within individual SWCNTs or SWCNT segments.…”

Recent Advances in Structure Separation of Single‐Wall Carbon Nanotubes and Their Application in Optics, Electronics, and Optoelectronics

“…[297] Recently, He et al introduced deep-trap states through the reaction of chirality-separated SWCNTs with various aryl functionalization agents, and thus achieved the tunable room-temperature single-photon emission at telecom wavelengths (Figure 17c). [308] These pioneering works have attracted great attentions, and stimulated extensive researches on the mechanisms, property, and applications of covalent functionalization of singlechirality SWCNTs, [275,[296][297][298][299][308][309][310][311][312][313][314][315][316][317][318][319][320][321][322][323][324][325][326] facilitating the development of SWCNT-based single-photon emission.…”

“…systematically investigated the influence of covalent defects on charge transport within a functionalized (6, 5) SWCNT network and revealed that the defect‐derived EL emission could be tuned through the defect density. [ 322 ] These findings facilitated the development of high‐performance SWCNT‐based EL devices.…”

Absolute Quantification of sp3 Defects in Semiconducting Single-Wall Carbon Nanotubes by Raman Spectroscopy

“…The maximum ensemble PLQY is observed at fairly low levels of functionalization, which would be favorable for electrically pumped light-emitting devices. 15 In contrast, single-photon emission requires exactly one luminescent defect per SWCNT. 1 Hence, accurate control over the degree of functionalization and knowledge of the precise sp 3 defect densities are highly desired for further optimization.…”