Operationally Stable Ultrathin Organic Field Effect Transistors Based on Siloxane Dimers of Benzothieno[3,2-b][1]Benzothiophene Suitable for Ethanethiol Detection

Ultrathin organic field effect transistors (OFETs) demonstrate great potential as highly sensitive gas sensors since its electrical performance strongly depends on the environment. However, fabrication of high performance OFETs with reliable operational stability for continuous measurements by fast, rather simple, and inexpensive technique is still a challenge. Herein, electrical and sensing properties of ultrathin OFETs based on siloxane dimers of benzothieno[3,2-b][1]benzothiophene (BTBT) with different aliphatic spacer lengths fabricated by Langmuir-Blodgett, Langmuir-Schaefer (LS) or spin-coating techniques are studied, compared and optimized. Investigation of the influence of interface dielectric layer on electrical performance and operational stability of the devices allowed obtaining uniform low-defect ultrathin semiconducting layers responsible for improved electrical performance. Field-effect mobility up to 0.47 cm(2) V-1 s(-1) is achieved for the devices based on the dimer with undecylenic spacer between the BTBT core and disiloxane central fragment fabricated by LS method on the top of poly(methyl methacrylate) interface layer. Promising operational stability lead to advanced sensory properties demonstrated by sensing of ethanethiol with the limit of detection of 30 ppb in the humid air, which is a record value for portable sensing technologies.

Automated summary

This study investigates the electrical and sensing properties of ultrathin OFETs based on BTBT dimers with different aliphatic spacer lengths, fabricated by Langmuir-Blodgett, Langmuir-Schaefer, or spin-coating techniques. By optimizing the interface dielectric layer, uniform low-defect ultrathin semiconducting layers are obtained, resulting in improved electrical performance. The highest field-effect mobility of 0.47 cm(2) V-1 s(-1) is achieved for devices fabricated by LS method on top of a poly(methyl methacrylate) interface layer. The promising operational stability leads to advanced sensory properties, with a record limit of detection of 30 ppb for sensing ethanethiol in humid air.