Influence of Injection Barrier on Vertical Organic Field Effect Transistors.

Organic field-effect transistors (OFETs) have shown great potential for applications that require low temperature deposition on large and flexible substrates. To increase their performance, in particular a high transconductance and transit frequency, the transistor channel length has to be scaled into the submicrometer regime, which can be easily achieved in vertical organic field effect transistors (VOFETs). However, despite high performance observed in VOFETs, these transistors usually suffer from short channel effects like weak saturation of the drain current and direct source-drain leakage resulting in large off currents.

Finding the equilibrium of organic electrochemical transistors.

Organic Electrochemical Transistors are versatile sensors that became essential for the field of organic bioelectronics. However, despite their importance, an incomplete understanding of their working mechanism is currently precluding a targeted design of Organic Electrochemical Transistors and it is still challenging to formulate precise design rules guiding materials development in this field. Here, it is argued that current capacitive device models neglect lateral ion currents in the transistor channel and therefore fail to describe the equilibrium state of Organic Electrochemical Transistors.

Poly(ethylene glycol) Diacrylate Based Electro-Active Ionic Elastomer.

Preparation and low voltage induced bending (converse flexoelectricity) of crosslinked poly(ethylene glycol) diacrylate (PEGDA), modified with thiosiloxane (TS) and ionic liquid (1-hexyl-3-methylimidazolium hexafluorophosphate) (IL) are reported. In between 2µm PEDOT:PSS electrodes at 1 V, it provides durable (95% retention under 5000 cycles) and relatively fast (2 s switching time) actuation with the second largest strain observed so far in ionic electro-active polymers (iEAPs). In between 40 nm gold electrodes under 8 V DC voltage, the film can be completely curled up (270° bending angle) with 6% strain that, to the best of the knowledge, is unpreceded among iEAPs.

Electroresponsive Ionic Liquid Crystal Elastomers.

This paper describes the preparation, physical properties, and electric bending actuation of a new class of active materials-ionic liquid crystal elastomers (iLCEs). It is demonstrated that iLCEs can be actuated by low-frequency AC or DC voltages of less than 1 V. The bending strains of the unoptimized first iLCEs are already comparable to the well-developed ionic electroactive polymers.

Doped bottom-contact organic field-effect transistors.

The influence of doping on doped bottom-gate bottom-contact organic field-effect transistors (OFETs) is discussed. It is shown that the inclusion of a doped layer at the dielectric/organic semiconductor layer leads to a significant reduction in the contact resistances and a fine control of the threshold voltage. Through varying the thickness of the doped layer, a linear shift of threshold voltage V from -3.

Tuning charge carrier transport and optical birefringence in liquid-crystalline thin films: A new design space for organic light-emitting diodes.

Liquid-crystalline organic semiconductors exhibit unique properties that make them highly interesting for organic optoelectronic applications. Their optical and electrical anisotropies and the possibility to control the alignment of the liquid-crystalline semiconductor allow not only to optimize charge carrier transport, but to tune the optical property of organic thin-film devices as well. In this study, the molecular orientation in a liquid-crystalline semiconductor film is tuned by a novel blading process as well as by different annealing protocols.

Contact Resistance Effects in Highly Doped Organic Electrochemical Transistors.

Injection at the source contact critically determines the behavior of depletion-type organic electrochemical transistors (OETs). The contact resistance of OETs increases exponentially with the gate voltage and strongly influences the modulation of the drain current by the gate voltage over a wide voltage range. A modified standard model accounting contact resistance can explain the particular shape of the transconductance.