Due to relatively low charge‐carrier mobilities in organic materials, high operational voltages often have to be applied and result in severe limitations. While it has been reported that elastic ...polymeric dielectrics, containing a very low ion concentration, are able to overcome this bottleneck, a systematic study on the working mechanisms and their implications for sensors is still missing. Due to the possibility to form a double‐layer capacitor while maintaining high insulating properties, such dielectrics enable stable low‐voltage devices, giving access to high current output and high on/off ratio even below 0.5 V. Field‐effect transistor devices are used to characterize this novel class of materials and to unravel their working mechanisms. To address their capability for sensors, a proof‐of‐concept experiment is performed, i.e., photoresponse is characterized and the field‐effect dependence is analyzed. Stable low‐voltage operation is a crucial issue, especially for biosensor applications which typically operate in physiological liquids and are limited by the small electrochemical window of water.
Double‐layer dielectrics maintain high insulating properties, enable stable low‐voltage field‐effect transistors, giving access to high current output and high on/off ratio even below 0.5 V. High stability in aqueous media is shown as well as gate dependent photoresponse enabling tunable sensitivity. Stable low‐voltage operation is important for biosensors, which operate in physiological liquids and are limited by the small electrochemical window of water.
Deformable electronic devices that are impervious to mechanical influence when mounted on surfaces of dynamically changing soft matters have great potential for next–generation implantable ...bioelectronic devices. Here, deformable field–effect transistors (FETs) composed of single organic nanowires (NWs) as the semiconductor are presented. The NWs are composed of fused thiophene diketopyrrolopyrrole based polymer semiconductor and high–molecular–weight polyethylene oxide as both the molecular binder and deformability enhancer. The obtained transistors show high field–effect mobility >8 cm2 V–1 s–1 with poly(vinylidenefluoride–co–trifluoroethylene) polymer dielectric and can easily be deformed by applied strains (both 100% tensile and compressive strains). The electrical reliability and mechanical durability of the NWs can be significantly enhanced by forming serpentine–like structures of the NWs. Remarkably, the fully deformable NW FETs withstand 3D volume changes (>1700% and reverting back to original state) of a rubber balloon with constant current output, on the surface of which it is attached. In conclusion, the deformable transistors can robustly operate without noticeable degradation on a mechanically dynamic soft matter surface, e.g., a pulsating balloon (pulse rate: 40 min–1 (0.67 Hz) and 40% volume expansion) that mimics a beating heart, which underscores its potential for future biomedical applications.
The chemical modification of an immobilized single crystal in a fluid cell is reported, whereby a material with switching functions is generated
in situ
by generating a chemical reagent in the flow. ...Crystals of the insulating organic crystal of TCNQ (tetracyanoquinodimethane) were grown in a microfluidic channel and were trapped using a pneumatic valve, a nascent technique for materials manipulation. They were subsequently reduced using solution-deposited silver to provide a conducting material
in situ
by a heterogeneous reaction. Removal of the new material from the chip proved it to be the silver salt of reduced TCNQ. Uniquely, conducting atomic force microscope (CAFM) studies show three regions in the solid. The localized original neutral organic material crystal is shown to be an insulator but to produce areas with Ohmic conducting characteristics after reduction. This inhomogeneous doping provides an opportunity for probing electrical materials properties side by side. Measurements with the CAFM witness this conducting material where the TCNQ is fully transformed to the silver salt. Additionally, an intermediate phase is observed that exhibits bipolar resistive switching typical of programmable resistive memories. Raman microscopy proves the conversion of the material in specific regions and clearly defines the intermediate phase region that could be responsible for the switching effect in related materials. This kind of "on crystal chemistry" exploiting immobilization and masking by a pneumatic clamp in a microfluidic channel shows how material can be selectively converted to give different functionalities in the same material piece, even though it is not a single crystal to single crystal conversion, and beckons exploitation for the preparation of systems relevant for molecular electronics as well as other areas where chemical manipulation of single crystals could be beneficial.
The chemical modification of an immobilized single crystal in a fluid cell is reported, whereby a material with switching functions is generated with reagent in the stream.
The chemical modification of an immobilized single crystal in a fluid cell is reported, whereby a material with switching functions is generated with reagent in the stream.
The chemical modification ...of an immobilized single crystal in a fluid cell is reported, whereby a material with switching functions is generated
in situ
by generating a chemical reagent in the flow. Crystals of the insulating organic crystal of TCNQ (tetracyanoquinodimethane) were grown in a microfluidic channel and were trapped using a pneumatic valve, a nascent technique for materials manipulation. They were subsequently reduced using solution-deposited silver to provide a conducting material
in situ
by a heterogeneous reaction. Removal of the new material from the chip proved it to be the silver salt of reduced TCNQ. Uniquely, conducting atomic force microscope (CAFM) studies show three regions in the solid. The localized original neutral organic material crystal is shown to be an insulator but to produce areas with Ohmic conducting characteristics after reduction. This inhomogeneous doping provides an opportunity for probing electrical materials properties side by side. Measurements with the CAFM witness this conducting material where the TCNQ is fully transformed to the silver salt. Additionally, an intermediate phase is observed that exhibits bipolar resistive switching typical of programmable resistive memories. Raman microscopy proves the conversion of the material in specific regions and clearly defines the intermediate phase region that could be responsible for the switching effect in related materials. This kind of “on crystal chemistry” exploiting immobilization and masking by a pneumatic clamp in a microfluidic channel shows how material can be selectively converted to give different functionalities in the same material piece, even though it is not a single crystal to single crystal conversion, and beckons exploitation for the preparation of systems relevant for molecular electronics as well as other areas where chemical manipulation of single crystals could be beneficial.
Three new organic semiconductors, in which either two methoxy units are directly linked to a dibenzotetrathiafulvalene (DB‐TTF) central core and a 2,1,3‐chalcogendiazole is fused on the one side, or ...four methoxy groups are linked to the DB‐TTF, have been synthesised as active materials for organic field‐effect transistors (OFETs). Their electrochemical behaviour, electronic absorption and fluorescence emission as well as photoinduced intramolecular charge transfer were studied. The electron‐withdrawing 2,1,3‐chalcogendiazole unit significantly affects the electronic properties of these semiconductors, lowering both the HOMO and LUMO energy levels and hence increasing the stability of the semiconducting material. The solution‐processed single‐crystal transistors exhibit high performance with a hole mobility up to 0.04 cm2 V−1 s−1 as well as good ambient stability.
Fused flat: Rigid electron donor–acceptor conjugates with tetrathiafulvalene (TTF) as an electron donor and 2,1,3‐benzochalcogendiazole as an electron acceptor have been prepared (see figure). Together with tetramethoxy‐substituted dibenzo‐TTF, a detailed study of their electronic properties is described. The solution‐processed single‐crystal transistors based on these π‐extended TTF derivatives exhibit high performance as well as good ambient stability.
The chemical modification of an immobilized single crystal in a fluid cell is reported, whereby a material with switching functions is generated
by generating a chemical reagent in the flow. Crystals ...of the insulating organic crystal of TCNQ (tetracyanoquinodimethane) were grown in a microfluidic channel and were trapped using a pneumatic valve, a nascent technique for materials manipulation. They were subsequently reduced using solution-deposited silver to provide a conducting material
by a heterogeneous reaction. Removal of the new material from the chip proved it to be the silver salt of reduced TCNQ. Uniquely, conducting atomic force microscope (CAFM) studies show three regions in the solid. The localized original neutral organic material crystal is shown to be an insulator but to produce areas with Ohmic conducting characteristics after reduction. This inhomogeneous doping provides an opportunity for probing electrical materials properties side by side. Measurements with the CAFM witness this conducting material where the TCNQ is fully transformed to the silver salt. Additionally, an intermediate phase is observed that exhibits bipolar resistive switching typical of programmable resistive memories. Raman microscopy proves the conversion of the material in specific regions and clearly defines the intermediate phase region that could be responsible for the switching effect in related materials. This kind of "on crystal chemistry" exploiting immobilization and masking by a pneumatic clamp in a microfluidic channel shows how material can be selectively converted to give different functionalities in the same material piece, even though it is not a single crystal to single crystal conversion, and beckons exploitation for the preparation of systems relevant for molecular electronics as well as other areas where chemical manipulation of single crystals could be beneficial.
A compact and planar donor-acceptor molecule 1 comprising tetrathiafulvalene (TTF) and benzothiadiazole (BTD) units has been synthesised and experimentally characterised by structural, optical, and ...electrochemical methods. Solution-processed and thermally evaporated thin films of 1 have also been explored as active materials in organic field-effect transistors (OFETs). For these devices, hole field-effect mobilities of µFE=(1.3±0.5)×10-3 and (2.7±0.4)×10-3cm2Vs-1 were determined for the solution-processed and thermally evaporated thin films, respectively. An intense intramolecular charge-transfer (ICT) transition at around 495nm dominates the optical absorption spectrum of the neutral dyad, which also shows a weak emission from its ICT state. The iodine-induced oxidation of 1 leads to a partially oxidised crystalline charge-transfer (CT) salt {(1)2I3}, and eventually also to a fully oxidised compound {1I3}1/2I2. Single crystals of the former CT compound, exhibiting a highly symmetrical crystal structure, reveal a fairly good room temperature electrical conductivity of the order of 2Scm-1. The one-dimensional spin system bears compactly bonded BTD acceptors (spatial localisation of the LUMO) along its ridge.
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