Organic thin-film transistors with inkjet-printed electrodes on hydrophobic Teflon-AF gate dielectric with reversible surface properties

Naderi, Paria; Grau, Gerd

doi:10.1016/j.orgel.2022.106612

Cited by 7 publications

(5 citation statements)

References 51 publications

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“…where g m , W, L, C ox , and µ 0 are transconductance, transistor width and length, dielectric capacitance per unit area (here SiO 2 ), and low-field mobility, respectively. Using the transfer characteristics in the linear regime (V d = −2 V) and from the slope and the yintercept of Y versus V g , µ 0 and V t are extracted [50,51]. Later, using equation ( 2), and by extracting the…”

Section: Resultsmentioning

confidence: 99%

Inkjet-printed transistors with coffee ring aligned carbon nanotubes

Naderi,

Grau

2024

Flex. Print. Electron.

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Low-concentration deposition techniques such as inkjet printing for forming carbon nanotube (CNT) transistor channels typically result in higher on-off current ratio, while lowering the field-effect mobility compared to traditional high-concentration techniques. In this paper, we show that inkjet-printed devices can have both high field-effect mobility and on-off current ratio by utilizing coffee ring induced thickness variation in the channel. The coffee ring effect occurs naturally in printed patterns with most solvents and substrates, and it pushes dissolved particles to the edges of printed features. Thickness variation and coffee ring effect are usually avoided in the channel of solution processed TFTs by implementing additional expensive steps in the fabrication process. Instead, here, we control these variations and utilize them to create inkjet-printed CNT channels with printing induced thickness variation that improves transistor properties. Printing properties such as printing speed, and number of layers are studied to manipulate capillary flow and form thicker line edges, which ultimately enhance current transport in the CNT network. A two-pass printing pattern with separate lines improves the field-effect mobility five times compared to a pattern with connected lines that has no defined edges. The field-effect mobility increases from 1.1 to 5.7 cm2/V.s at a drain voltage of -2 V.

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Section: Resultsmentioning

confidence: 99%

Inkjet-printed transistors with coffee ring aligned carbon nanotubes

Naderi,

Grau

2024

Flex. Print. Electron.

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“…Printed electronics can produce various electronic thin-film devices, including diodes [1,2], capacitors [3], resistors [4,5], solar cells [6,7], sensors [8,9], batteries [10], antennas [11,12], and transistors [13][14][15]. Some advantages of printing methods are the possibility of printing over large areas, cost reduction, and rapid manufacturing [16,17].…”

Section: Introductionmentioning

confidence: 99%

Pattern-dependent resistivity variations in inkjet-printed conductors due to non-uniform ink drying

Ghalamboran,

Nazeri,

Grau

2024

Flex. Print. Electron.

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When fabricating inkjet-printed electronic devices and circuits, inkjet-printed conductive materials require drying and sintering to improve electrical conductivity. Electrical conductivity should be the same irrespective of pattern design, size, location, or density of adjacent patterns. However, we demonstrate that spatial variations in the drying process for inkjet-printed patterns with proximity to others cause resistivity variations. These resistivity variations are studied here experimentally for different circuit patterns and in arrays of inkjet-printed square electrodes. This variation depends not only on the location of each electrode in an array but also on the number of electrodes. This means that for the same drying temperature and duration, the array with a larger number of electrodes exhibits a larger resistivity variation. The sooner an electrode dries, the lower resistivity it achieves. The resistivity variation between an individual electrode and the center electrode in a 7×7 electrode array can be a factor of seven. This variation decreases for lower numbers of electrodes to a factor of three for a 3×3 array. Furthermore, X-ray Photoelectron Spectroscopy (XPS) analyses provide evidence for the residual presence of carbon-based materials within electrodes after the drying process. These results confirm that the location of electrodes within an array significantly influences the amount of residual carbon-based materials, thereby contributing to resistivity variations. Although intense pulsed light (IPL) sintering can decrease this variation, its optimal parameters depend on the printed designs, and our simulation results show a non-uniform temperature profile over the electrode arrays. Temperature increases more at the center of patterns than the corners, which can be useful in this case to improve resistivity uniformity. In this study, for the first time, we show how different printed shapes and designs can result in non-uniform resistivity after drying and sintering.

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“…[7,8] Additionally, fluoropolymers are ideal materials for use as the gate dielectric in organic thin-film transistors (OTFTs) often printed with silver nanoparticle inks, or similar. [5,[9][10][11][12] Fluoropolymers are advantageous due to their low dielectric constants enhancing charge transport, [9] and characteristic water repellence, which also acts as encapsulation and prevents doping. [12,13] Plasma/UV treatment of hydrophobic surfaces is one of the most common methods to enable printing on such substrates by rendering them hydrophilic, with many studies using this technique to develop and study printing on hydrophobic substrates.…”

Section: Introductionmentioning

confidence: 99%

“…[1][2][3] Inkjet printing has allowed patterns to be printed on a variety of surfaces ranging from paper to Teflonamorphous fluoropolymer (AF) with plasma pretreatment. [4,5] While the printability and ink behavior have been well documented for hydrophilic surfaces allowing users to achieve uniform connected lines, the characteristic low surface energy of hydrophobic substrates creates significant challenges for printing, especially for non-contact printing techniques, e.g., inkjet printing.…”

Section: Introductionmentioning

confidence: 99%

Inkjet Printing on Hydrophobic Surface: Practical Implementation of Stacked Coin Strategy

Docherty,

Naderi,

Grau

et al. 2024

Adv Eng Mater

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While inkjet printing on many hydrophilic surfaces can be achieved through control of drop spacing and droplet deposition delay alone, the same for hydrophobic substrates prove to be challenging. The low surface energies of hydrophobic surfaces lead to dewetting, unwanted coalescence of wet drops, and bulging, preventing intact and uniform lines of low‐viscosity ink to form. In this paper, we have adapted the stacked coin strategy, a well‐established and successful technique for hydrophilic surfaces, for use on hydrophobic surfaces. Stacked coin morphology occurs when the time taken to deposit a subsequent overlapping droplet in a pattern is longer than the evaporation time of the prior droplet. On hydrophobic surfaces, it is considerably more challenging and the parameter window for successful printing is smaller than on hydrophilic surfaces, thus requiring in‐depth study to implement this methodology on hydrophobic surfaces. We conducted experiments using a custom‐built inkjet printer with variable stage speed and stage temperature, where silver nanoparticle ink was used to print on Teflon‐AF substrates. Our study identified the following regimes: isolated droplets, isolated multi‐droplets, broken line, true stacked coin, and delamination. The relationship between substrate temperature, drop spacing and droplet deposition delay controls the printability window of true stacked coin morphology and its surrounding regimes. The key to the success of this strategy on hydrophobic surfaces is rapid drying of individual droplets to minimize movement due to hydrophilic coalescence of overlapping dried and wet droplets. Our study identified 180⁰C as the critical temperature for instantaneous drying of the studied ink, and a maximum drop spacing of 20µm.This article is protected by copyright. All rights reserved.

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Organic thin-film transistors with inkjet-printed electrodes on hydrophobic Teflon-AF gate dielectric with reversible surface properties

Cited by 7 publications

References 51 publications

Inkjet-printed transistors with coffee ring aligned carbon nanotubes

Inkjet-printed transistors with coffee ring aligned carbon nanotubes

Pattern-dependent resistivity variations in inkjet-printed conductors due to non-uniform ink drying

Inkjet Printing on Hydrophobic Surface: Practical Implementation of Stacked Coin Strategy

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