Hydrogenated Graphene Based Organic Thin Film Transistor Sensor for Detection of Chloride Ions as Corrosion Precursors

Corrosion monitoring and management has been at the center of structural health monitoring protocols due to its damaging effects on metallic structures. Current corrosion prevention and management programs often fail to include environmental factors such as Cl− ions and surface wetness. Early detection of these environmental factors can prevent the onset of corrosion and reduce repair and maintenance-related expenses. There is growing interest in creating solution-processed thin film environmental sensors with high sensitivity to corrosion precursors, low-cost fabrication, and small footprint, rendering them viable candidates for investigation as potential corrosion sensors that could be easily integrated into existing structures and screen printed or patterned directly into surface coatings. In this work, we have implemented C60-based n-type organic thin film transistors (OTFTs) with functionalized graphene oxide for humidity sensing and functionalized graphene nanoparticles for Cl− ion detection, using low-cost solution processing techniques. The reduced graphene oxide (rGO)-coated OTFT humidity sensor is designed for the qualitative estimation of surface moisture levels and high levels of humidity, and it exhibits a relative responsivity for dry to surface wetness transition of 122.6% to surface wetness, within a response time of 20 ms. We furthermore implemented an in-house synthesized hydrogenated graphene coating in conjunction with a second OTFT architecture for Cl− ions sensing which yielded a sensitivity of 4%/ppm to ultrafine ionic concentrations, over an order of magnitude lower than the range identified to cause corrosion in aircraft structures.

Organic monolayers modified by vacuum ultraviolet irradiation for solution-processed organic thin-film transistors

A trimethylsilyl-monolayer modified by vacuum ultraviolet (VUV) light has been investigated for use in solution-processed organic thin-film transistors (OTFTs). The VUV irradiation changed a hydrophobic trimethylsilyl-monolayer formed from hexamethyldisilazane vapor into a hydrophilic surface suitable for solution processing. The treated surface was examined via water contact angle measurement and X-ray photoelectron spectroscopy. An appropriate irradiation of VUV light enabled the formation of a dioctyl[1]benzothieno[3,2-b][1]benzothiophene (C8-BTBT) film on a modified monolayer by spin-coating. Consequently, the C8-BTBT-based OTFT with a monolayer modified for an optimal VUV irradiation time exhibited a field-effect mobility up to 4.76 cm2 V−1 s−1. The partial monolayer modification with VUV can be adapted to a variety of solution-processes and organic semiconductors for prospective printed electronics.

Hybrid La2O3-cPVP Dielectric for Organic Thin Film Transistor Applications

In this work, we have studied the electrical performance of cross-linked polyvinyl phenol (cPVP) modified lanthanum oxide (La2O3) bilayer dielectric film in pentacene thin film transistors (TFT). A simple spin-coating and room temperature operated cross-linking reaction of the hydroxyl moieties of PVP and the nitrogen groups of PMF were carried out to form the cross-linked PVP. The deposition of a thin 30 nm cPVP layer over the La2O3 layer provided a low leakage current (<10−7A/cm2), causing a reduction in the interface trap density. Besides, the modified surface properties of the La2O3 layer were favorable for the growth of pentacene organic semiconductors. As a result, the current on-off ratio and the sub-threshold slope was improved from 104 and 1.0 V/decade to 105 and 0.67 V/decade. The La2O3∕cPVP pentacene TFT operated at −10 V also exhibited improvement in the field-effect mobility to 0.71 cm2/Vs from 0.48 cm2/Vs for the single-layer La2O3 (130 nm) device. Thus, our work demonstrates that the rare earth oxide La2O3 with cPVP is an excellent dielectric system in the context of emerging transistors with hybrid polymer gate dielectrics.

Processing–Structure–Performance Relationship in Organic Transistors: Experiments and Model

In this paper, organic thin film transistors with different configurations are fabricated, and the effect on their performance when tailoring the semiconductor/insulator and semiconductor/contact interfaces through suitable treatments is analyzed. It is shown that the admittance spectroscopy used together with a properly developed electrical model turns out to be a particularly appropriate technique for correlating the performance of devices based on new materials in the manufacturing methods. The model proposed here to describe the equivalent metal–insulator–semiconductor (MIS) capacitor enables the extraction of a wide range of parameters and the study of the physical phenomena occurring in the transistors: diffusion of mobile ions through the insulator, charge trapping at the interfaces, dispersive transport in the semiconductor, and charge injection at the metal contacts. This is necessary to improve performance and stability in the case, like this one, of a novel organic semiconductor being employed. Atomic force microscopy images are also exploited to support the relationship between the semiconductor morphology and the electrical parameters.

Highlighting the processing versatility of a silicon phthalocyanine derivative for organic thin-film transistors

Silicon phthalocyanine (SiPc) derivatives have recently emerged as promising materials for n-type organic thin-film transistors (OTFTs) with the ability to be fabricated either by solid state or solution processes through...