Abstract
The organic material soluble polyimide (PI) and organic–inorganic hybrid PI–barium titanate (BaTiO3) nanoparticle dielectric materials (IBX, where X is the concentration of BaTiO3 nanoparticles in a PI matrix) were successfully synthesized through a sol–gel process. The effects of various BaTiO3 contents on the hybrid film performance and performance optimization were investigated. Furthermore, pentacene-based organic thin film transistors (OTFTs) with PI-BaTiO3/polymethylmethacrylate or cyclic olefin copolymer (COC)-modified gate dielectrics were fabricated and examined. The hybrid materials showed effective dispersion of BaTiO3 nanoparticles in the PI matrix and favorable thermal properties. X-ray diffraction patterns revealed that the BaTiO3 nanoparticles had a perovskite structure. The hybrid films exhibited high formability and planarity. The IBX hybrid dielectric films exhibited tunable insulating properties such as the dielectric constant value and capacitance in ranges of 4.0–8.6 and 9.2–17.5 nF cm−2, respectively. Adding the modified layer caused the decrease of dielectric constant values and capacitances. The modified dielectric layer without cross-linking displayed a hydrophobic surface. The electrical characteristics of the pentacene-based OTFTs were enhanced after the surface modification. The optimal condition for the dielectric layer was 10 wt% hybrid film with the COC-modified layer; moreover, the device exhibited a threshold voltage of 0.12 V, field-effect mobility of 4.32 × 10−1 cm2 V−1 s−1, and on/off current of 8.4 × 107.
Highlights
Organic thin film transistors (OTFTs) have attracted considerable attention in recent years for their unique features, including low fabrication costs [1,2,3,4,5], flexibility [6, 7], and ease of processing in solution [8]
Using the hybrid materials of high-dielectric-constant BaTiO3 nanoparticles in the PI matrix as gate dielectric materials can improve the performance of OTFT devices
The IBX hybrid materials were fabricated as the gate dielectrics of the OTFT devices
Summary
Organic thin film transistors (OTFTs) have attracted considerable attention in recent years for their unique features, including low fabrication costs [1,2,3,4,5], flexibility [6, 7], and ease of processing in solution [8]. Relevant research has sought to improve OTFT performance in organic and polymeric semiconductors by modifying their chemical structures [9,10,11,12]. Other approaches, such as controlling the deposition of crystalline organic films [13,14,15] and controlling the nature of the interfaces, have been developed [16, 17]. Many polymeric dielectric materials have been applied as the dielectric materials in OTFTs, such as poly(styrene), poly(methyl methacrylate), poly(ethylene), poly(urethane), poly(vinyl alcohol), and poly(vinyl pyridine). To improve the electric characteristics and operational stability of OTFTs, the gate dielectric layers were modified with hydroxyl-free polymer insulators such as polymethylmethacrylate (PMMA) and cyclic olefin copolymer (COC)
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