All Publications

  • Impact of Side Chain Hydrophilicity on Packing, Swelling and Ion Interactions in Oxy-bithiophene Semiconductors. Advanced materials (Deerfield Beach, Fla.) Siemons, N., Pearce, D., Cendra, C., Yu, H., Tuladhar, S. M., Hallani, R. K., Sheelamanthula, R., LeCroy, G. S., Siemons, L., White, A. J., Mcculloch, I., Salleo, A., Frost, J. M., Giovannitti, A., Nelson, J. 2022: e2204258


    Exchanging hydrophobic alkyl-based side chains to hydrophilic glycol-based side chains is a widely adopted method for improving mixed-transport device performance, despite the impact on solid state packing and polymer-electrolyte interactions being poorly understood. Presented here is a Molecular Dynamics (MD) force field for modelling alkoxylated and glycolated polythiophenes. The force field is validated against known packing motifs for their monomer crystals. MD simulations, coupled with X-ray Diffraction (XRD), show that alkoxylated polythiophenes will pack with a 'tilted stack' and straight interdigitating side chains, whilst their glycolated counterpart will pack with a 'deflected stack' and an s-bend side chain configuration. MD simulations reveal water penetration pathways into the alkoxylated and glycolated crystals - through the pi-stack and through the lamellar stack respectively. Finally, the two distinct ways tri-ethylene glycol polymers can bind to cations are revealed, showing the formation of a meta-stable single bound state, or an energetically deep double bound state, both with a strong side chain length dependance. The minimum energy pathways for the formation of the chelates are identified, showing the physical process through which cations can bind to one or two side chains of a glycolated polythiophene, with consequences for ion transport in bithiophene semiconductors. This article is protected by copyright. All rights reserved.

    View details for DOI 10.1002/adma.202204258

    View details for PubMedID 35946142

  • Tuning Organic Electrochemical Transistor Threshold Voltage using Chemically Doped Polymer Gates. Advanced materials (Deerfield Beach, Fla.) Tan, S. T., Lee, G., Denti, I., LeCroy, G., Rozylowicz, K., Marks, A., Griggs, S., McCulloch, I., Giovannitti, A., Salleo, A. 2022: e2202359


    Organic electrochemical transistors (OECTs) have shown promise as transducers and amplifiers of minute electronic potentials due to their large transconductances. Tuning OECT threshold voltage is important to achieve low-powered devices with amplification properties within the desired operational voltage range. However, traditional design approaches have struggled to decouple channel and materials properties from threshold voltage, thereby compromising on several other OECT performance metrics such as electrochemical stability, transconductance, and dynamic range. In this work, we utilize simple solution processing methods to chemically dope polymer gate electrodes, thereby controlling their work function, which in turn tunes the operation voltage range of OECTs without perturbing their channel properties. Chemical doping of initially air-sensitive polymer electrodes further improves their electrochemical stability in ambient conditions. Thus, we demonstrate, for the first time, OECTs which are simultaneously low-powered and electrochemically resistant to oxidative side reactions at ambient conditions. This approach shows that threshold voltage, which was once interwoven with other OECT properties, can in fact be an independent design parameter, expanding the design space of OECTs. This article is protected by copyright. All rights reserved.

    View details for DOI 10.1002/adma.202202359

    View details for PubMedID 35737653

  • Critical analysis of self-doping and water-soluble n-type organic semiconductors: structures and mechanisms JOURNAL OF MATERIALS CHEMISTRY C Cowen, L. M., Gilhooly-Finn, P. A., Giovannitti, A., LeCroy, G., Demetriou, H., Neal, W., Dong, Y., Westwood, M., Luong, S., Fenwick, O., Salleo, A., Heutz, S., Nielsen, C. B., Schroeder, B. C. 2022

    View details for DOI 10.1039/d2tc01108e

    View details for Web of Science ID 000801023700001

  • Mixed Ionic-Electronic Conduction, a Multifunctional Property in Organic Conductors. Advanced materials (Deerfield Beach, Fla.) Tan, S. T., Gumyusenge, A., Quill, T. J., LeCroy, G. S., Bonacchini, G. E., Denti, I., Salleo, A. 2022: e2110406


    Organic mixed ionic-electronic conductors (OMIECs) have gained recent interest and rapid development due to their versatility in diverse applications ranging from sensing, actuation and computation to energy harvesting/storage, and information transfer. Their multifunctional properties arise from their ability to simultaneously participate in redox reactions as well as modulation of ionic and electronic charge density throughout the bulk of the material. Most importantly, the ability to access charge states with deep modulation through a large extent of its density of states and physical volume of the material enables OMIEC-based devices to display exciting new characteristics and opens up new degrees of freedom in device design. Leveraging the infinite possibilities of the organic synthetic toolbox, this perspective highlights several chemical and structural design approaches to modify OMIECs' properties important in device applications such as electronic and ionic conductivity, color, modulus, etc. Additionally, the ability for OMIECs to respond to external stimuli and transduce signals to myriad types of outputs has accelerated their development in smart systems. This perspective further illustrates how various stimuli such as electrical, chemical, and optical inputs fundamentally change OMIECs' properties dynamically and how these changes can be utilized in device applications.

    View details for DOI 10.1002/adma.202110406

    View details for PubMedID 35434865

  • Redox-Active Polymers Designed for the Circular Economy of Energy Storage Devices ACS ENERGY LETTERS Tan, S., Quill, T. J., Moser, M., LeCroy, G., Chen, X., Wu, Y., Takacs, C. J., Salleo, A., Giovannitti, A. 2021; 6 (10): 3450-3457
  • Ion Pair Uptake in Ion Gel Devices Based on Organic Mixed Ionic-Electronic Conductors ADVANCED FUNCTIONAL MATERIALS Quill, T. J., LeCroy, G., Melianas, A., Rawlings, D., Thiburce, Q., Sheelamanthula, R., Cheng, C., Tuchman, Y., Keene, S. T., McCulloch, I., Segalman, R. A., Chabinyc, M. L., Salleo, A. 2021
  • A Stacked Hybrid Organic/Inorganic Electrochemical Random-Access Memory for Scalable Implementation ADVANCED ELECTRONIC MATERIALS Tuchman, Y., Quill, T. J., LeCroy, G., Salleo, A. 2021