Bartlomiej Kolodziejczyk

Over the last two decades, there has been substantial development in the manufacturing of nano‐ and micro‐ tubes and wires as building blocks for electronic devices, such as field‐effect transistors, to complement the conventional semiconductor transistors in electronic circuits. Previous attempts to improve device performance through the development of new materials have focused mostly on carbon or metal oxide‐based semiconducting materials. Here, we report a flexible conducting polymer micro‐wire grown from the vapor phase via an oxidative polymerization route. Electrical measurements show that the single micro‐wires have relatively high conductivity and non‐linear electrical characteristics. In addition, we demonstrate the fabrication of a flexible polythiophene micro‐wire organic electrochemical transistor, in which the channel and gate are made of single micro‐wires. These devices are fully compatible with conventional fabrication processes and operate in the sub‐volt regime, and have the potential to be scaled to larger multi‐micro‐wire architectures and circuits. This study demonstrates the concept of self‐assembly of organic molecules and simultaneous polymerization to generate complex, ordered, and functional structures resembling polymerized Bechgaard salts.

In this study, we combine a photochemical cell with a transistor, forming a novel optical-to-electronic interface using OECTs with a light-sensitive gate, which can be used for photonic, optogenetic and other applications where conversion from an optical to electronic signal is key.

Most of the techniques used for micro and nano‐patterning currently are of high quality and reproducibility, but they require expensive equipment and involve many time‐consuming steps to achieve the desired results. We herein report a patterning method of conducting layers on breathable substrates using a fast, simple, and mask‐less laser engraving technique. A resolution in the range of 30 μm has been successfully achieved in this report. The method is fast and the pattern can be easily changed or redesigned within a few minutes. The patterning time for a 25 cm² sample is approximately 3 minutes. In comparison, patterning a sample of the same size using photolithography requires up to 4 hours. In this manuscript, we describe the laser patterning process, how to improve the patterning resolution, the calibration steps involved as well as an application for organic electrochemical transistors as gas sensors for detecting oxygen or sulphur dioxide. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42359.

Ordered hetero-junctions using one dimensional inorganic nanostructures have been widely studied to develop devices such as high efficiency photovoltaic devices, light emitting diodes, catalysts, supercapacitors, lithium ion batteries and nanogenerators. High quality Schottky contacts can be obtained by the spin coating of conducting polymer dispersions/solutions onto inorganic nanostructures; however, the interaction of polar surfaces of the nanostructures with chemically active materials in the spin coating solution makes the junctions less reliable. In the present work, we show that high quality junctions can be fabricated by either directly growing the nanostructures onto the vapour phase polymerised (VPP) poly(3,4-ethylenedioxythiophene) (PEDOT) substrates or sandwiching VPP polymerised substrates, thereby avoiding any unwanted interactions with the acidic additives from the polymer solution at the organic–inorganic interfaces. The I–V measurements proved that the direct growth of ZnO NWs on PEDOT coated substrates creates an ohmic contact, whereas the PEDOT layer on top surface produces a Schottky contact due to the dipole moment with the polar ends.

This work is the further development of the previous pH (effective) sensor work where a biologically derived proton-active redox centre – riboflavin (RFN) – was entrapped into a vapour phase polymerised poly(3,4-ethylenedioxythiophene) film and ferrocene (Fc) dissolved in the sample solution was used as an internal reference redox couple. Here, we report a disposable solid state pH (effective) sensor where we successfully incorporated both RFN and Fc into a single solid state electrode. The electrodes were then used for pH (effective) sensing where water is not required. The system was further miniaturised and simplified from a 3 electrode to a 2 electrode setup with the working electrode area being as small as 0.09 mm². The sensors show the ability to measure pH (effective) in both aqueous and non-aqueous media including ionic liquids (ILs) regardless of their hydrophobicity. This is an important step towards the ability to customise ILs or non-aqueous media with suitable proton activity (PA) for various applications e.g. customised ILs for biotechnological applications such as protein preservation and customised media for PA dependent reactions such as catalytic reactions.

The discovery of a new poly(3,4-ethylenedioxythiophene) (PEDOT) composite with unique memory characteristics has led to the demonstration of durable Organic ElectroChemical Transistors (OECT) based memory devices. The composites of PEDOT with polytetrahydrofuran undergo a structural collapse during electrochemical reduction that requires approximately 800 mV overpotential to re-open and is thus hindering the re-oxidation of the composite. This effect causes the composite at intermediate potentials to be able to have two different oxidation states and thereby resistances, depending on the “on” or “off” switching potential applied prior to the intermediate potential. Notably, this hysteresis is lasting over time and no drift has been observed. Impedance spectroscopy, in-situ UV-Vis spectroscopy, conductivity measurement, in-situ electrochemical quartz crystal microbalance, and differential scanning calorimetry were used to confirm and explain the switching memory phenomena. The OECT platform was used to validate the PEDOT:PTHF as a one-pot memory source-drain material where a threefold increase in drain current was observed between “off” and “on” mode of the transistor after modulation of the Ag/AgCl gate.

It has been a persistent challenge to develop ordered conducting polymer nano- and micro-structures with a high active area. We herein report the method to produce and characterise a network of nanometre-sized walls (nano-walls) which forms on the surface of a conducting co-polymer composite film based on bithiophene and terthiophene prepared using vapour-phase polymerisation (VPP). The density and dimension of the walls are tunable in order to suit the application demands. The presence of nano-walls on the film surface increases the capacitance of the coating up to 3.4 times, making it a very promising candidate for energy and organic electronics applications. The nano-walls have also proved to be great candidates for photonic applications, efficiently guiding light. A two-step growth mechanism is proposed, which includes the reduction of Fe(III) and part of the tosylate ligands in the Fe(III) para-toluene sulphonate oxidant. This is the first report of a self-assembling conducting polymer material with nano-wall features induced by the conditions during VPP.

It is shown that the absorption properties in the visible region of polymer films based on mixtures of terthiophene and bithiophene may be tailored to suit the needs of optical devices such as solar cells, sensors and organic light emitting diodes. Using vapor phase polymerization (VPP) with iron(III) p-toluenesulfonate as the oxidant, the optimised films exhibit an extended absorption band in both directions when compared to films based only on bithiophene or terthiophene. Cyclic voltammetry reveals new bands not observed before in addition to redox bands attributed to both poly(terthiophene) and poly(bithiophene). The polymer chain length and conjugation length were estimated using Raman and UV-vis spectroscopy.