Phenanthroline Additives for Enhanced Semiconducting Carbon Nanotube Dispersion Stability and Transistor Performance

Abstract

Dispersions of purely semiconducting single-walled carbon nanotubes (SWCNTs) have enabled solution-processed SWCNT networks as active layers in field-effect transistors (FETs) with high carrier mobilities and excellent on/off current ratios. Although reproducibility has improved in recent years, reaching the level that is required for commercial large-scale processing remains a challenge. A key issue is the tendency of SWCNTs to aggregate over time, resulting in network inhomogeneities that cause large device performance variations. Based on the tailored formulation of colloidal inks by the choice of solvent and use of additives, we demonstrate the strong stabilization effect of phenanthroline additives on polymer-sorted (6,5) SWCNT using time-dependent near-infrared absorption spectroscopy as a fast and simple assessment tool for the aggregation rate. The addition of the N-heteropolycycle 1,10-phenanthroline significantly extends the stability of dispersions of polymer-wrapped nanotubes in toluene and hence improves the morphology of spin-coated networks even after ink storage for several days. Bottom-contact, top-gate FETs based on such networks show much higher charge carrier mobilities and drastically reduced device-to-device variations compared to devices based on SWCNT dispersions without phenanthroline. Nanotube ink formulations with small-molecule additives are an important step toward reproducible device parameters and are crucial for the translation of nanotube FETs from the laboratory to commercial applications.

Luminescent Defects in Single‐Walled Carbon Nanotubes for Applications

“…The emission intensity increased exponentially with current, which is consistent with exciton formation by impact excitation. [127,153] Defect electroluminescence resulting from electron-hole recombination in ambipolar light-emitting field-effect transistors was shown by Zorn et al [154] Top-gate/bottom-contact transistors with dense networks of semiconducting nanotubes and a poly(methyl methacrylate)/HfO x gate dielectric (see Figure 4a-c) had been previously shown to enable highly reproducible ambipolar charge transport [155][156][157] and the formation of a very controlled recombination and emission zone within the channel. [158][159][160] Networks of polymer-sorted (6,5) SWCNTs with covalent bromoaryl defects showed decreasing hole and electron mobilities with increasing defect density (quantified by the D/G Raman ratios), indicating their role as charge traps.…”

Networks of as-dispersed, polymer-wrapped (6,5) single-walled carbon nanotubes for selective Cu2+ and glyphosate sensing

“…After removal of unbound polymer, drop-cast networks of SWNTs were applied as the active transducing layers in water-gated transistors and investigated in terms of their sensing capabilities toward various metal ions. The copolymer PFO-BPy wraps almost exclusively (6,5) SWNTs, while PFO yields a mixture of nanotubes consisting predominantly of (7,5) SWNTs and small amounts of (6,5) and (7,6) SWNTs (see also ESI, Fig. S1 †).…”

“…Dispersions of purely semiconducting single-walled carbon nanotubes (SWNTs) are suitable inks for the creation of active thin films in a wide range of (opto-)electronic devicesespecially field-effect transistorsusing various solution processing techniques such as ink-jet printing, 1,2 aerosol jet printing [3][4][5][6] or even just spin-coating 7 or dip-coating. 8 Excellent semiconducting purities above 99.9% are attainable with modern separation and selective dispersion techniques.…”

Endohedral Filling Effects in Sorted and Polymer-Wrapped Single-Wall Carbon Nanotubes

“…Certainly, due to the high solubility of the alkane or dye molecule in the surrounding organic solvent, this is a difficult process to follow. Nevertheless, taking into account that the polymer extraction method is probably now the most convenient technique to obtain semiconducting SWCNTs − with device-relevant purity, − it is important to consider that endohedral filling may also alter the extraction result, especially since the method currently suffers from unexplainable low yields and when the result of extraction is strongly batch-dependent. , To this end, we use aqueous-based techniques to prepare small- and large-diameter SWCNTs that are either empty, water-filled, or alkane-filled and use these as a pseudo raw soot for polymer extraction. The separation result of samples with a highly uniform endohedral environment allows us to understand “real-world” extractions using raw soot.…”