Parylene-C-based flexible organic thin-film transistors and their reliability improvement using SU-8 passivation

Flexible and biocompatible organic thin-film transistors (OTFTs) can be well-suited for biological applications due to their compatibility with biomaterials. In this study, flexible OTFTs were fabricated with a Parylene-C substrate and gate dielectric, a material known for its flexibility and biocompatibility. We used poly[2,5-bis(3-tetradecylthiophen-2-yl)thieno[3,2-b]thiophene] as organic channel material. To ensure the longevity and protection of the channel, SU-8, known for its biocompatibility and transparency, effectively safeguarded the OTFT and ensured its sustained operation. Flexible OTFTs were affixed to a curved fixture, referred to as a “curved condition.” The device parameters at −20 V of V D in the curved condition shows an I o n / o f f ratio of 3.5 × 10⁴, threshold voltage ( V T H ) of −0.42 V, and mobility of 0.003 cm²/V s. The Parylene-C-based OTFT with SU-8 passivation demonstrated reliability by maintaining performance under curved conditions for 40 days. The results show that the proposed device is suitable for flexible electronics and sensor applications.