Solution-processable and photocurable aromatic polyurea gate dielectrics for high-performance organic thin-film transistors

Abstract

A solution-processable and photocurable polyurea (PU) with excellent electrical and dielectric properties is synthesized, characterized, and applied as a gate dielectric in high-performance organic thin-film transistors (OTFTs). The PU is synthesized from toluene-2,4-diisocyanate and 3,5-diaminobenzyl cinnamate via a condensation reaction. The PU containing cinnamoyl groups is photo-crosslinked without a photoinitiator and easily micropatterned by selective ultra-violet (UV) exposure. The photo-crosslinked PU (c-PU) film improves dielectric properties and thermal and chemical resistance compared with pristine PU films. We fabricated dinaphtho[2,3-b:2′,3′-f]thieno[3,2-b]thiophene (DNTT)-based OTFTs with a c-PU gate dielectric layer to investigate the performance of the c-PU thin film as a gate dielectric. The field-effect mobility and on/off ratio of DNTT-based OTFTs with surface-treated c-PU gate dielectric are 0.75 ± 0.03 cm2 V−1s−1 and 1.60 × 106, respectively. In addition, solution-processed diketopyrrolopyrrole-thienothiophene copolymer-based OTFTs with c-PU gate dielectric show field-effect mobility of 0.07 ± 0.01 cm2 V−1s−1 and on/off ratio of 2.88 × 105. Furthermore, the complementary inverter was successfully demonstrated by using c-PU with excellent insulating property as the gate dielectric.