Abstract
Since the first demonstration, the electrolyte-gated organic field-effect transistors (EGOFETs) have immediately gained much attention for the development of cutting-edge technology and they are expected to have a strong impact in the field of (bio-)sensors. However EGOFETs directly expose their active material towards the aqueous media, hence a limited library of organic semiconductors is actually suitable. By using two mostly unexplored strategies in EGOFETs such as blended materials together with a printing technique, we have successfully widened this library. Our benchmarks were 6,13-bis(triisopropylsilylethynyl)pentacene and 2,8-difluoro-5,11-bis(triethylsilylethynyl)anthradithiophene (diF-TES-ADT), which have been firstly blended with polystyrene and secondly deposited by means of the bar-assisted meniscus shearing (BAMS) technique. Our approach yielded thin films (i.e. no thicker than 30 nm) suitable for organic electronics and stable in liquid environment. Up to date, these EGOFETs show unprecedented performances. Furthermore, an extremely harsh environment, like NaCl 1M, has been used in order to test the limit of operability of these electronic devices. Albeit an electrical worsening is observed, our devices can operate under different electrical stresses within the time frame of hours up to a week. In conclusion, our approach turns out to be a powerful tool for the EGOFET manufacturing.
Highlights
Our approach consists of combining two widely overlooked strategies in the organic electronics operated in liquid: (i) the exploitation of blends composed by an insulating polymer and a small molecule organic semiconductor[13,21,22,23] and (ii) the use of a solution-shearing technique, such as bar-assisted meniscus shearing (BAMS), to deposit the OSC24,25
We have systematically studied the electrical performances of two soluble OSCs, namely diF-TES-ADT and TIPS-pentacene blended with polystyrene
These two materials have been extensively used up to date in organic electronics, this is the first report where they have been exploited in electrolyte-gated organic field effect transistors (EGOFETs)
Summary
A high degree of crystallinity along with an extended homogeneity at long-range length scales (i.e. from few to hundreds of μm) is fundamental to avoid the so-called “electrochemical doping”, whose distinctive fingerprints are a marked hysteresis, electrical instability within time frame of minutes and/or hours and slow operational response[17] With this in mind, spin-coated semi-crystalline or liquid crystalline polymer OSCs1,18 have been chosen as active layers in EGOFETs as well as single crystals[1] or thin films[14,19,20] of small molecule semiconductors prepared by vacuum sublimation. Our approach consists of combining two widely overlooked strategies in the organic electronics operated in liquid: (i) the exploitation of blends composed by an insulating polymer and a small molecule organic semiconductor[13,21,22,23] and (ii) the use of a solution-shearing technique, such as bar-assisted meniscus shearing (BAMS), to deposit the OSC24,25. This proves how our approach can be successfully exploited in the field of EGOFETs paving the way towards more complex technological platforms
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