Stretchable electronics exhibit unique mechanical properties to expand the applications areas of conventional electronics based on rigid wafers. Intrinsically stretchable thin film transistor is an ...essential component for functional stretchable electronics, which presents a great opportunity to develop mechanically compliant electronic materials. Certain elastomers have been recently adopted as the gate dielectrics, but their dielectric properties have not been thoroughly investigated for such applications. Here, a charging measurement technique with a resistor–capacitor circuit is proposed to quantify the capacitance of the dielectric layers based on elastomers. As compared with conventional methods, the technique serves as a universal approach to extract the capacitance of various elastomers under static conditions, irrespective of the charging mechanisms. This technique also offers a facile approach to reliably quantify the mobility of thin film transistors based on elastomeric dielectrics, paving the way to utilize this class of dielectrics in the development of intrinsically stretchable transistors.
A charging measurement technique is introduced as a universal approach to quantify the capacitance of elastomeric dielectrics. It reveals elastomers may either behave as conventional rigid polymer dielectrics or solid‐state electrolyte, with distinctive capacitance values and scaling relations. The development allows the mobility values of corresponding thin film transistors to be accurately determined, which is essential for the development of instrinsically stretchable transistors.
Tetrathiafulvalenes (TTFs) are an appealing class of organic small molecules giving rise to some of the highest performing active materials reported for organic field effect transistors (OFETs). ...Because they can be easily chemically modified, TTF‐derivatives are ideal candidates to perform molecule–property correlation studies and, especially, to elucidate the impact of molecular and crystal engineering on device performance. A brief introduction into the state‐of‐the‐art of the field‐effect mobility values achieved with TTF derivatives employing different fabrication techniques is provided. Following, structure–performance relationships are discussed, including polymorphism, a phenomenon which is crucial to control for ensuring device reproducibility. It is also shown that chemical modification of TTFs has a strong influence on the electronic structure of these materials, affecting their stability as well as the nature of the generated charge carriers, leading to devices with p‐channel, n‐channel, or even ambipolar behaviour. TTFs have also shown promise in other applications, such as phototransistors, sensors, or as dopants or components of organic metal charge transfer salts used as source–drain contacts. Overall, TTFs are appealing building blocks in organic electronics, not only because they can be tailored to perform fundamental studies, but also because they offer a wide spectrum of potential applications.
Tetrathiafulvalenes are promising active materials in organic field‐effect transistors (OFETs), in which they exhibit high performances. An overview is provided of the use of this family of materials as a model building block for OFETs to highlight general concepts of organic semiconductors and their use in devices.
To date, crystallization studies conducted in space laboratories, which are prohibitively costly and unsuitable to most research laboratories, have shown the valuable effects of microgravity during ...crystal growth and morphogenesis. Herein, an easy and highly efficient method is shown to achieve space‐like experimentation conditions on Earth employing custom‐made microfluidic devices to fabricate 2D porous crystalline molecular frameworks. It is confirmed that experimentation under these simulated microgravity conditions has unprecedented effects on the orientation, compactness and crack‐free generation of 2D porous crystalline molecular frameworks as well as in their integration and crystal morphogenesis. It is believed that this work will provide a new “playground” to chemists, physicists, and materials scientists that desire to process unprecedented 2D functional materials and devices.
How to achieve simulated microgravity conditions on Earth? The art of growing and processing 2D porous crystalline molecular frameworks in simulated microgravity is presented.
Both high gain and transconductance at low operating voltages are essential for practical applications of organic field-effect transistors (OFETs). Here, we describe the significance of the ...double-layer capacitance effect in polar rubbery dielectrics, even when present in a very low ion concentration and conductivity. We observed that this effect can greatly enhance the OFET transconductance when driven at low voltages. Specifically, when the polar elastomer poly(vinylidene fluoride-co-hexafluoropropylene) (e-PVDF-HFP) was used as the dielectric layer, despite a thickness of several micrometers, we obtained a transconductance per channel width 30 times higher than that measured for the same organic semiconductors fabricated on a semicrystalline PVDF-HFP with a similar thickness. After a series of detailed experimental investigations, we attribute the above observation to the double-layer capacitance effect, even though the ionic conductivity is as low as 10(-10) S/cm. Different from previously reported OFETs with double-layer capacitance effects, our devices showed unprecedented high bias-stress stability in air and even in water.
Conductive polymer composites based on nanostructured particular fillers have many important applications, such as temperature and pressure sensors. Among many factors, the microstructure of ...conductive particle network determines the electron conduction properties. It has been found that nanospiky Ni particles filled in a polymer matrix can enable a reversible and rapid response and a large change of conductivity upon temperature change. While it has been previously hypothesized that quantum tunneling plays an important role, no direct experimental evidence with systematic characterization and understanding is available. Herein, impedance spectroscopy and low‐temperature electrical measurements are used to reveal the charge transport mechanisms of nanospiky Ni‐based nanocomposites upon temperature change. The results show that quantum tunneling effects indeed play a major role, which enables significant interparticle resistance change upon slight change (expansion and contraction) of the microstructured particle network.
Pyroresistive polymer composites, composed of a polymeric matrix with nanostructured fillers, allow extremely high thermoresponsivity. Impedance spectroscopy and low‐temperature measurements reveal the charge transport mechanisms of nanospiky Ni‐based nanocomposites identifying quantum tunneling effects, which enable significant interparticle resistance changes upon slight expansion or contraction of the microstructured particle network.
Solution prepared single crystal organic field‐effect transistors (OFETs) combine low‐cost with high performance due to structural ordering of molecules. However, in organic crystals polymorphism is ...a known phenomenon, which can have a crucial influence on charge transport. Here, the performance of solution‐prepared single crystal OFETs based on two different polymorphs of dithiophene‐tetrathiafulvalene, which were investigated by confocal Raman spectroscopy and X‐ray diffraction, are reported. OFET devices prepared using different configurations show that both polymorphs exhibited excellent device performance, although the α‐phase revealed charge carrier mobility between two and ten times higher in accordance to the closer stacking of the molecules.
Abstract A set of unique features, including large-area solution processing on flexible and stretchable substrates, make polymer semiconductors a promising material choice for a range of ...state-of-the-art applications in electronics, optoelectronics and sensing. Yet, an inherent weakness of polymer semiconductors remains their low dielectric constants, increasing their susceptibility toward unscreened dipoles. These dipoles are particularly prevalent at polymer-dielectric interfaces with high- k dielectrics, which are essential for the operation of devices such as low-voltage field-effect transistors. This shortcoming can be addressed by using self-assembled monolayers (SAMs) to passivate surfaces that impact charge transport. However, SAM-treatment also increases the hydrophobicity of surfaces and therefore poses a challenge for subsequent solution processing steps and complex packaging of devices. Here, we report low-voltage polymer transistors processed by spin coating of the polymer semiconductors on highly hydrophobic SAM-treated aluminum and hafnium oxide dielectrics (contact angles >100) through fine-tuning of the interfacial tension at the polymer-dielectric interface. This approach enables the processing and detailed characterization of near-amorphous (indacenodithiophene- co benzothiadiazole) as well as semicrystalline ( poly(2,5-bis(2-octyldodecyl)-3,6-di(thiophen-2-yl)diketopyrrolo3,4-cpyrrole-1,4-dione-alt-thieno3,2-bthiophen )) polymer semiconductors. We demonstrate polymer transistors that exhibit high on-currents and field-independent, charge carrier mobilities of 0.8 cm 2 V −1 s −1 at low operating voltages (<3 V).
Our work examines the structural-electronic correlation of a new curcuminoid, AlkCCMoid, as a dielectric material on different substrates. For this purpose, we show a homemade sublimation method that ...allows the direct deposition of molecules on any type of matrix. The electronic properties of AlkCCMoid have been evaluated by measurements on single crystals, microcrystalline powder, and sublimated samples, respectively. GIWAXS studies on surfaces and XRD studies on powder have revealed the existence of polymorphs and the effect that substrates have on curcuminoid organization. We describe the dielectric nature of our system and identify how different polymorphs can affect electronic parameters such as permittivity, all corroborated by DFT calculations.
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•A new curcuminoid with triple bonds ending groups shows dielectric behavior•Direct sublimation of the curcuminoid on substrates is achieved under mild conditions•Structural-electronic correlation on surfaces is a strong analytical tool•Permittivity is greatly affected by polymorphism
Chemistry; Crystallography; Supramolecular chemistry; Surface science
High levels of performance and stability have been demonstrated for conjugated polymer thin-film transistors in recent years, making them promising materials for flexible electronic circuits and ...displays. For sensing applications, however, most research efforts have been focusing on electrochemical sensing devices. Here we demonstrate a highly stable biosensing platform using polymer transistors based on the dual-gate mechanism. In this architecture a sensing signal is transduced and amplified by the capacitive coupling between a low-
bottom dielectric and a high-
ionic elastomer top dielectric that is in contact with an analyte solution. The new design exhibits a high signal amplification, high stability under bias stress in various aqueous environments, and low signal drift. Our platform, furthermore, while responding expectedly to charged analytes such as the protein bovine serum albumin, is insensitive to changes of salt concentration of the analyte solution. These features make this platform a potentially suitable tool for a variety of biosensing applications.
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