Organic Field-Effect Transistors Based on a Liquid-Crystalline Polymeric Semiconductor using SU-8 Gate Dielectrics onFlexible Substrates

Abstract

In this work, the insulating properties of poly(4-vinylphenol) (PVP) and SU-8 (MicroChem, Westborough, MA, USA) dielectrics are analyzed and compared with each other. We further investigate the performance behavior of organic field-effect transistors based on a semiconducting liquid-crystal polymer (LCP) using both dielectric materials and evaluate the results regarding the processability. Due to the lower process temperature needed for the SU-8 deposition, the realization of organic transistors on flexible substrates is demonstrated showing comparable charge carrier mobilities to devices using PVP on glass. In addition, a µ-dispensing procedure of the LCP on SU-8 is presented, improving the switching behavior of the organic transistors, and the promising stability data of the SU-8/LCP stack are verified after storing the structures for 60 days in ambient air showing negligible irreversible degradation of the organic semiconductor.

SynCells: A 60 × 60 μm2 Electronic Platform with Remote Actuation for Sensing Applications in Constrained Environments

“…While SU-8 is commonly used as a passivation layer, 44 it has only been sporadically explored as a gate dielectric in transistors. 49 The transistors have an On/Off ratio of 10 6 and exhibit a hysteresis of about 6 V. The average on-current is about 2 μA/μm, and the average mobility is 2.2 cm 2 /(V s). This is lower than stateof-the-art MoS 2 transistors 47,50−52 but still better than organic semiconductors and amorphous silicon.…”

“…The MoS 2 transistors on the SynCells are 8 μm wide and 1.5 μm long and are placed on a gold back-gate with an 800 nm thick SU-8 layer that forms the gate dielectric. SU-8 was used for this function because it is chemical resistant, mechanically flexible, and easy to pattern and has a high dielectric strength (see Supporting Figure S6). While SU-8 is commonly used as a passivation layer, it has only been sporadically explored as a gate dielectric in transistors .…”

“…SU-8 was used for this function because it is chemical resistant, mechanically flexible, and easy to pattern and has a high dielectric strength (see Supporting Figure S6). While SU-8 is commonly used as a passivation layer, it has only been sporadically explored as a gate dielectric in transistors . The transistors have an On/Off ratio of 10 6 and exhibit a hysteresis of about 6 V. The average on-current is about 2 μA/μm, and the average mobility is 2.2 cm 2 /(V s).…”

Homogeneous Crystallization of Micro-DispensedTIPS-Pentacene Using a Two-Solvent System toEnable Printed Inverters on Foil Substrates

“…This could be due to a variety of reasons including the choice of the SU-8 dielectric as well as the crystal ordering during the drying process. Increased hysteresis issues have been identified in the transfer curves in prior investigations using a semiconducting polymer due to charge traps at the semiconductor/dielectric interface originated from dielectric surface functionalities, adsorbed small molecules at the interface or structural defects of the semiconductor [19]. The absence of a hysteresis indicates a well-ordered layer of the TIPS-pentacene at the semiconductor/dielectric interface with minor defects and thus low density of charge carrier trapping sites.…”

Epoxy Based Ink as Versatile Material for Inkjet-Printed Devices

“…We are convinced that epoxy based ink is an appropriate functional material due to its excellent film-forming properties as demonstrated in the first part of this work. Moreover, ink shows other interesting properties such as low temperature processing (around 100 °C), good chemical resistance, wettability, low leakage current density, dielectric constant about 3, 41 and high breakdown electric field (evaluated at 3 mV.cm −1 ).…”