Polymer-Sorted Semiconducting Carbon Nanotube Networks for High-Performance Ambipolar Field-Effect Transistors

Abstract

Efficient selection of semiconducting single-walled carbon nanotubes (SWNTs) from as-grown nanotube samples is crucial for their application as printable and flexible semiconductors in field-effect transistors (FETs). In this study, we use atactic poly(9-dodecyl-9-methyl-fluorene) (a-PF-1-12), a polyfluorene derivative with asymmetric side-chains, for the selective dispersion of semiconducting SWNTs with large diameters (>1 nm) from plasma torch-grown SWNTs. Lowering the molecular weight of the dispersing polymer leads to a significant improvement of selectivity. Combining dense semiconducting SWNT networks deposited from an enriched SWNT dispersion with a polymer/metal-oxide hybrid dielectric enables transistors with balanced ambipolar, contact resistance-corrected mobilities of up to 50 cm2·V–1·s–1, low ohmic contact resistance, steep subthreshold swings (0.12–0.14 V/dec) and high on/off ratios (106) even for short channel lengths (<10 μm). These FETs operate at low voltages (<3 V) and show almost no current hysteresis. The resulting ambipolar complementary-like inverters exhibit gains up to 61.

Nanoscale Charge Percolation Analysis in Polymer‐Sorted (7,5) Single‐Walled Carbon Nanotube Networks

“…The sorted (7,5) SWNTs were dispersed from a mixture of nanotube chirality by exploiting the interaction between the nanotube and the side-chains attached to the PFO backbone. [18] It has F. Bottacchi et al Small (2016), DOI: 10.1002/smll.201600922 -5 -been previously shown that polyfluorene and its derivatives have the ability to selectively wrap and solubilize semiconducting SWNTs with specific diameters.…”

“…From AFM measurements, the nanotube length in the as-processed (7,5) SWNTs network is found to range from ~100 nm to ~1500 nm, with a SWNT surface density well above the percolation threshold and a maximum surface coverage ≈ 58%. Analysis of the field-effect charge transport measurements in the SWNT network using a two-dimensional -2 -plane and reveal the isotropic nature of the as-spun (7,5) SWNT networks.…”

“…Over the last several years, semiconducting single-walled carbon nanotubes (SWNTs) have been employed in a wide range of optoelectronic devices, including field-effect transistors [1][2][3][4][5][6] (FETs), solar cells, [7] integrated circuits, [8][9][10] radio frequency ID (RFID) antennas [11] and lightemitting devices. [12,13] In addition to their attractive electronic properties, SWNTs can be easily solution-processed, hence making them extremely attractive for application in plastic microelectronics.…”

“…Here, we report a new method based on the combination of different characterization techniques, which enables the quantification of residual metallic nanotubes content in a highly pure (7,5) SWNT network. Polymer [poly(9,9-di-n-octylfluorenyl-2,7-diyl)] (PFO) was used to disperse and select the (7,5) semiconducting SWNTs from a mixture of nanotube chirality.…”

“…Polymer [poly(9,9-di-n-octylfluorenyl-2,7-diyl)] (PFO) was used to disperse and select the (7,5) semiconducting SWNTs from a mixture of nanotube chirality. Fieldeffect transistors based on a dense random network of polymer-sorted (7,5) SWNTs deposited from solution at room temperature, show primarily p-channel behavior with weak electron accumulation depending on the gate dielectric and device geometry chosen.…”