Solution-Processed Flexible Gas Barrier Films for Organic Field-Effect Transistors

Abstract

The solution-processed gas barrier film was fabricated and used for organic field-effect transistors (OFETs). Organic-inorganic hybrid sol-gel materials and cyclic transparent optical polymer (CYTOP) were used as the bottom and top layers of the barrier films, respectively, to effectively protect against gas permeation through the barrier films. The organic-inorganic hybrid material includes sol-gel precursors and amphiphilic polymers. The conventional sol-gel precursors form siloxane bonds by sol-gel reaction and form densely-packed rigid part in thin films. The alkoxysilane-functionalized amphiphilic polymer in the sol-gel precursor solutions has two hydrophobic segments and a hydrophilic segment. The amphiphilic polymer with reactive alkoxysilane groups at both ends of the hydrophobic segments can be involved in the sol-gel reaction, and they can act as surfactants to surround the conventional precursors stabilizing the nanoparticles formed by the hydrolytic condensation reaction of precursors. The amphiphilic polymer also provides flexibility for hybrid sol-gel thin films. CYTOP was used to introduce hydrophobicity on top of the organic-inorganic hybrid thin films. The barrier films containing the organic-inorganic hybrid and hydrophobic CYTOP layers were applied to OFETs and exhibited notable gas barrier properties, high transparency, and flexibility. The encapsulated OFETs with 6,13-bis(triisopropylsilylethynyl)pentacene (TIPS-pentacene) as an organic semiconductor showed a slight decrease in hole mobility from 0.13 to 0.11 cm2 V-1 s-1, while the OFETs without barrier films showed a mobility decrease from 0.11 to 0.03 cm2 V-1 s-1.