Flexible Indium‐Tin‐Oxide Homojunction Thin‐Film Transistors with Two In‐Plane Gates on Cellulose‐Nanofiber‐Soaked Papers

Abstract

to achieve low-voltage operation in TFTs. TFTs with ionic liquids or gel electrolytes as the gate dielectrics can electrostatically induce high-density carriers in the channel layer at a very low gate voltage due to the electric-double-layer (EDL) electrostatic coupling. [5] The application of regular paper for TFTs application is limited by its high surface roughness. In order to reduce the surface roughness, a thin passivation layer was coated on the regular paper. [6] However, the coating passivation layer may affect the porous structure of paper and may have a negative impact on the paper device. [7] Newly, cellulose nanofibers (CNFs), one of sources of biodegradable and recyclable materials, have achieved much attention due to their strong mechanical strength and excellent flexible property. [8] Nanopapers were produced based on cellulose nanofibers by physical or chemical methods, which had a much smaller diameter than regular paper. [9] Although TFTs on nanopaper substrates showed good performance, [7b,10] the method of nanopaper production was complicated and unsuited for mass production. Recently, cellulose nanofibers were used as the buffer layers and gate dielectric layers in TFTs fabrication, and good electrical performance was obtained. [11] Here, cellulose nanofibers-soaked weighing papers are simultaneously used as the gate dielectrics and substrates for TFTs fabrication. The operation voltage of such TFTs is reduced to ≈2.0 V due to the large EDL capacitance of the CNFs-soaked paper. The ITO-based homojunction TFTs exhibit good electrical performance and great mechanical stability. Furthermore, inverter and NAND logic operation are demonstrated with such TFTs. Such flexible TFTs on low-cost and biodegradable paper pave the way for the development of flexible portable applications.

Cellulose‐Based Flexible Functional Materials for Emerging Intelligent Electronics

“…c,d) Reproduced with permission. [ 113 ] Copyright 2019, Wiley‐VCH. e) Normalized maximum drain current of OTFT at different bending radii.…”

“…A flexible homojunction OTFT that used CNFs simultaneously as a gate dielectric and substrate is shown in Figure 7c. [ 113 ] Due to the large electric‐double‐layer capacitance of the CNF‐soaked paper, the homojunction OTFT had a low‐voltage operation of 2.0 V and a relatively high I on / I off ratio of 7.5 × 10 6 . No obvious electrical degradation was measured at various bending radii (Figure 7d).…”

Significance of Flexible Substrates for Wearable and Implantable Devices: Recent Advances and Perspectives

“…fabricated TFTs using the various techniques of drop‐casting, immersion, thermal evaporation, and sputtering. [ 215 ] The fabrication process involves the drop‐casting of the cellulose nanofiber solution on the weighing paper in the first step, followed by immersion in a CNF solution for 30 s. Following the sputtering of the indium tin oxide source/drain electrode on the opposite side of the immersed paper sheet by one‐step radiofrequency (RF) magnetron sputtering, a thin layer of Ag was thermally deposited on the CNF‐immersed paper sheet surface, thus resulting in flexible TFTs.…”

Biodegradable, Flexible, and Transparent Conducting Silver Nanowires/Polylactide Film with High Performance for Optoelectronic Devices

“…If the conventional nondegradable substrates (e.g., silicon, glass, and petroleum-based plastics) are replaced by biodegradable materials, the e-waste problem will be greatly alleviated. Nowadays, many natural renewable polymer materials such as cellulose, silk, chitin, and so on [8,9] have been applied as the substrate of various electronics (sensors [10-12], solar cells [13,14], transistors [15,16], and printed circuits [17,18]) owing to their apparent advantages of biodegradability, lightweight, and flexibility. Nevertheless, these natural polymer materials suffer from the drawbacks of high surface roughness, low mechanical strength, poor durability, inferior thermal resistance, bad shape stability in solution, and complex processing [19][20][21].…”