Transparent and Colorless Polyimides Containing Multiple Trifluoromethyl Groups as Gate Insulators for Flexible Organic Transistors with Superior Electrical Stability

Abstract

A suitable insulating polymer material that is compatible with the fabrication process of organic transistors and has excellent electrical properties is critically required for the nextgeneration flexible organic electronics. In this study, using a onestep polymerization method, we synthesized two different solutionprocessable polyimides (PIs) incorporated with abundant trifluoromethyl groups. Not only were the two resulting PIstermed 6FDA-6FDAM-PI and 6FDA-TFMB-PIwell soluble in organic solvents, but also they showed transparent and colorless optical properties. The fluorinated PI films showed smooth surface topographies and surface energy values that were appropriate for their use in bottom-gate organic transistors. Organic transistors separately fabricated with 6FDA-6FDAM-PI and 6FDA-TFMB-PI as the gate insulators showed excellent device performance and electrical stability under various testing conditions, especially for pentacene-based devices. The excellent performance of the devices with fluorinated PIs was attributed to the enhanced microstructure of the organic semiconductor and the fluorine-rich characteristic of the underlying gate insulator. Furthermore, organic complementary circuits including the basic logic gates of NOT, NOR, and NAND were demonstrated using these devices.

Preparation of Meldrum's acid‐functionalized polyimides exhibiting organo‐soluble, reactive, self‐crosslinkable, and colorless features

“…The mechanical properties of PI(MADA-6FDA) are superior over the reported cPIs and comparable to the properties of Kapton. 11,37,38 Crosslinking the PI(MADA-6FDA) sample further enhances the mechanical properties, as CRPI(MADA-6FDA) exhibits a tensile strength, an elongation at break, and a Young's Modulus of 79.7 MPa, 5.4%, and 2267 MPa, respectively. Additional properties of CRPI(MADA-6FDA) are discussed in the following sessions for a comparison with nanocomposites of CRPI(MADA-6FDA) and silica nanoparticles.…”

“…Colorless PIs (cPIs) therefore receive massive research attention. 9,11,37,38 One of the beneficial molecular design for cPIs is incorporation of polar/crosslinkable units and bulky/twisted substituents to cPIs for balancing their high thermal stability and high optical transparency, respectively. 11 As the chemical structure of MA unit meets the above criteria, the prepared MA-PIs are expected to demonstrate colorless characteristic.…”

Self-Assembled Monolayers: Versatile Uses in Electronic Devices from Gate Dielectrics, Dopants, and Biosensing Linkers

“…In the first section, we comprehensively recapitulate the important advances of SAMs in organic thin-film transistors (OTFTs) [4][5][6][7][8]. Since 1990, OTFTs have emerged as soft electronic devices with functional properties that include mechanical flexibility [9][10][11][12][13] and a solution-processed, facile manufacturing process [14,15]. However, the organic semiconductors in OTFTs are vulnerable to charge traps [16][17][18] and leakage current, which frequently occur in oxide dielectrics (i.e., silicon dioxide (SiO 2 ) [19][20][21], aluminum oxide (Al 2 O 3 ) [22,23], and hafnium oxide (HfO 2 ) [24]).…”

“…However, the organic semiconductors in OTFTs are vulnerable to charge traps [16][17][18] and leakage current, which frequently occur in oxide dielectrics (i.e., silicon dioxide (SiO 2 ) [19][20][21], aluminum oxide (Al 2 O 3 ) [22,23], and hafnium oxide (HfO 2 ) [24]). Owing to the strong susceptibility of Micromachines 2021, 12, 565 2 of 17 organic semiconductors to charge traps, OTFTs suffer from instability, which causes currentvoltage sweep hysteresis [25][26][27], shifts in the threshold voltage (V TH ) [28,29], and bias stress effects [30][31][32][33]. To address these issues, the treatment of the hydroxylated surfaces of dielectrics is crucial.…”

Colorless and transparent semi‐alicyclic polyimide films with intrinsic flame retardancy based on alicyclic dianhydrides and aromatic phosphorous‐containing diamine: Preparation and properties

“…Among the up‐to‐date efforts, incorporation of substituents or structures with less polarity, less conjugated skeleton, high electronegativity, and high molar volumes into the molecular structures of the conventional high‐temperature polymers seems to be most promising modification procedures. For example, a series of colorless and transparent PI (CPI) films with great potential applications in optoelectronic fabrication have been developed in the past decades via incorporation of either alicyclic units, 8‐10 fluoro‐containing substituents, 11‐13 or asymmetrical molecular structures 14 into the molecular chains. Semi‐alicyclic CPI and fluoro‐containing CPI films represent two of the most important commercially available optical PI films up to now.…”