Flexible small-channel thin-film transistors by electrohydrodynamic lithography

Abstract

Small-channel organic thin-film transistors (OTFTs) are an essential component of microelectronic devices. With the advent of flexible electronics, the fabrication of OTFTs still faces numerous hurdles in the realization of highly-functional, devices of commercial value. Herein, a concise and efficient procedure is proposed for the fabrication of flexible, small-channel organic thin-film transistor (OTFT) arrays on large-area substrates that circumvents the use of photolithography. By employing a low-cost and high-resolution mechano-electrospinning technology, large-scale micro/nanofiber-based patterns can be digitally printed on flexible substrates (Si wafer or plastic), which can act as the channel mask of TFT instead of a photolithography reticle. The dimensions of the micro/nanochannel can be manipulated by tuning the processing parameters such as the nozzle-to-substrate distance, applied voltage, and fluid supply. The devices exhibit excellent electrical properties with high mobilities (∼0.62 cm V s) and high on/off current ratios (∼2.47 × 10), and they are able to maintain stability upon being bent from 25 mm to 2.75 mm (bending radius) over 120 testing cycles. This electrohydrodynamic lithography-based approach is a digital, programmable, and reliable alternative for easily fabricating flexible, small-channel OTFTs, which can be integrated into flexible and wearable devices.

High‐Performance, Micrometer Thick/Conformal, Transparent Metal‐Network Electrodes for Flexible and Curved Electronic Devices

“…Both linear pattern and serpentine pattern ( Figure a) of photoresist can be collected during the simple linear motion of substrate by adjusting the parameters to fit the local spiraling phenomenon of photoresist jet, which is caused by the repulsion among charged jet fibers under high electric field. For the linear photoresist pattern, a short nozzle‐to‐substrate distance (H) is used to improve positioning via a high‐speed moving stage and avoid the influence of spiraling phenomenon . Oppositely, the “whipping/buckling” phenomenon of the electrospinning jet is used to directly fabricate serpentine pattern with diverse geometries in a programmable, accurately positioned, and individually controlled manner.…”

Large‐Scale Direct‐Writing of Aligned Nanofibers for Flexible Electronics

“…j) The mobility and ON/OFF ratio of the flexible transistors under different bending status. Reproduced with permission . Copyright 2017, Royal Society of Chemistry.…”

“…Meanwhile, nanofibers can be served as sacrificial masks to fabricate TFTs with nanoscale channel length and channel width . A single P 3 HT/PEO nanofiber FET with a ion‐gel dielectric of poly(styrene‐ block ‐methylmethacrylate‐ block ‐styrene) (PS‐PMMA‐PS) triblock copolymer in an ionic liquid, [EMIM][TFSI], shew a maximum carrier mobility of 9.7 cm 2 V −1 s −1 (average of 3.8 cm 2 V −1 s −1 ) and a high average I on / I off of 1.70 × 10 6 (fiber diameter: 309 nm, source/drain gap: ≈300 nm, shown in Figure d,e) .…”

“…A single P 3 HT/PEO nanofiber FET with a ion‐gel dielectric of poly(styrene‐ block ‐methylmethacrylate‐ block ‐styrene) (PS‐PMMA‐PS) triblock copolymer in an ionic liquid, [EMIM][TFSI], shew a maximum carrier mobility of 9.7 cm 2 V −1 s −1 (average of 3.8 cm 2 V −1 s −1 ) and a high average I on / I off of 1.70 × 10 6 (fiber diameter: 309 nm, source/drain gap: ≈300 nm, shown in Figure d,e) . The dimension of micro/nanochannel is programmable and easily manipulated by tuning the process parameters such as the nozzle‐to‐substrate distance, applied voltage, and fluid supply, and can be fabricated on both Si wafer and flexible plastic substrates (Figure h) . The flexible small‐channel organic TFT exhibits rather high mobility (0.62 cm 2 V −1 s −1 ) and I on / I off ratio (2.47 × 10 6 ), and excellent bending stability (120 cyclic bending tests of the device with a bending radius from 25 to 2.75 mm, shown in Figure i,j).…”

Patterning Micro-Nano Structures Based on Tip-Assisted Electrohydrodynamic Jet Printing

“…The fabrication of micro-nano patterned structures has attracted significant attention owing to its wide application in flexible electronic devices [1][2][3], micro-nano sensors [4,5], microelectromechanical systems [6], and biosensing detection [7,8]. So far, several techniques have been used in the fabrication of micro/nano-structures including inkjet printing [9], photolithography [10], laser processing [11], and screen printing [12].…”