All Publications

  • Role of aggregates and microstructure of mixed-ionic-electronic-conductors on charge transport in electrochemical transistors. Materials horizons LeCroy, G., Cendra, C., Quill, T. J., Moser, M., Hallani, R., Ponder, J. F., Stone, K., Kang, S. D., Liang, A. Y., Thiburce, Q., McCulloch, I., Spano, F. C., Giovannitti, A., Salleo, A. 2023


    Synthetic efforts have delivered a library of organic mixed ionic-electronic conductors (OMIECs) with high performance in electrochemical transistors. The most promising materials are redox-active conjugated polymers with hydrophilic side chains that reach high transconductances in aqueous electrolytes due to volumetric electrochemical charging. Current approaches to improve transconductance and device stability focus mostly on materials chemistry including backbone and side chain design. However, other parameters such as the initial microstructure and microstructural rearrangements during electrochemical charging are equally important and are influenced by backbone and side chain chemistry. In this study, we employ a polymer system to investigate the fundamental electrochemical charging mechanisms of OMIECs. We couple in situ electronic charge transport measurements and spectroelectrochemistry with ex situ X-ray scattering electrochemical charging experiments and find that polymer chains planarize during electrochemical charging. Our work shows that the most effective conductivity modulation is related to electrochemical accessibility of well-ordered, interconnected aggregates that host high mobility electronic charge carriers. Electrochemical stress cycling induces microstructural changes, but we find that these aggregates can largely maintain order, providing insights on the structural stability and reversibility of electrochemical charging in these systems. This work shows the importance of material design for creating OMIECs that undergo structural rearrangements to accommodate ions and electronic charge carriers during which percolating networks are formed for efficient electronic charge transport.

    View details for DOI 10.1039/d3mh00017f

    View details for PubMedID 37089107

  • An ordered, self-assembled nanocomposite with efficient electronic and ionic transport. Nature materials Quill, T. J., LeCroy, G., Halat, D. M., Sheelamanthula, R., Marks, A., Grundy, L. S., McCulloch, I., Reimer, J. A., Balsara, N. P., Giovannitti, A., Salleo, A., Takacs, C. J. 2023


    Mixed conductors-materials that can efficiently conduct both ionic and electronic species-are an important class of functional solids. Here we demonstrate an organic nanocomposite that spontaneously forms when mixing an organic semiconductor with an ionic liquid and exhibits efficient room-temperature mixed conduction. We use a polymer known to form a semicrystalline microstructure to template ion intercalation into the side-chain domains of the crystallites, which leaves electronic transport pathways intact. Thus, the resulting material is ordered, exhibiting alternating layers of rigid semiconducting sheets and soft ion-conducting layers. This unique dual-network microstructure leads to a dynamic ionic/electronic nanocomposite with liquid-like ionic transport and highly mobile electronic charges. Using a combination of operando X-ray scattering and in situ spectroscopy, we confirm the ordered structure of the nanocomposite and uncover the mechanisms that give rise to efficient electron transport. These results provide fundamental insights into charge transport in organic semiconductors, as well as suggesting a pathway towards future improvements in these nanocomposites.

    View details for DOI 10.1038/s41563-023-01476-6

    View details for PubMedID 36797383

  • meso-Ethynyl-extended push-pull type porphyrins for near-infrared organic photodetectors JOURNAL OF MATERIALS CHEMISTRY C Gielen, S., Cuesta Gomez, V., Brebels, S., Quill, T., Vanderspikken, J., Lutsen, L., de la Cruz, P., Vandewal, K., Langa, F., Maes, W. 2022

    View details for DOI 10.1039/d2tc00588c

    View details for Web of Science ID 000825688000001

  • Conjugated polymers for microwave applications: untethered sensing platforms and multifunctional devices. Advanced materials (Deerfield Beach, Fla.) Tan, S. T., Giovannitti, A., Marks, A., Moser, M., Quill, T. J., McCulloch, I., Salleo, A., Bonacchini, G. E. 2022: e2202994


    In the past two decades, organic electronic materials have enabled and accelerated a large and diverse set of technologies, from energy harvesting devices and electro-mechanical actuators, to flexible and printed (opto)electronic circuitry. Among organic (semi)conductors, mixed ionic-electron conductors (OMIECs) are now at the center of renewed interest in organic electronics, as they are key drivers of recent developments in the fields of bioelectronics, energy storage, and neuromorphic computing. However, due to the relatively slow switching dynamics of organic electronics, their application in microwave technology, until recently, has been overlooked. Nonetheless, other unique properties of OMIECs, such as their substantial electrochemical tunability, charge modulation range and processability, make this field of use ripe with opportunities. In this work, we demonstrate the use of a series of solution-processed intrinsic OMIECs to actively tune the properties of metamaterial-inspired microwave devices, including an untethered bioelectrochemical sensing platform that requires no external power, and a tunable resonating structure with independent amplitude- and frequency-modulation. These devices showcase the considerable potential of OMIEC-based metadevices in autonomous bioelectronics and reconfigurable microwave optics. This article is protected by copyright. All rights reserved.

    View details for DOI 10.1002/adma.202202994

    View details for PubMedID 35759573

  • Efficient Electronic Tunneling Governs Transport in Conducting Polymer-Insulator Blends. Journal of the American Chemical Society Keene, S. T., Michaels, W., Melianas, A., Quill, T. J., Fuller, E. J., Giovannitti, A., McCulloch, I., Talin, A. A., Tassone, C. J., Qin, J., Troisi, A., Salleo, A. 2022


    Electronic transport models for conducting polymers (CPs) and blends focus on the arrangement of conjugated chains, while the contributions of the nominally insulating components to transport are largely ignored. In this work, an archetypal CP blend is used to demonstrate that the chemical structure of the non-conductive component has a substantial effect on charge carrier mobility. Upon diluting a CP with excess insulator, blends with as high as 97.4 wt % insulator can display carrier mobilities comparable to some pure CPs such as polyaniline and low regioregularity P3HT. In this work, we develop a single, multiscale transport model based on the microstructure of the CP blends, which describes the transport properties for all dilutions tested. The results show that the high carrier mobility of primarily insulator blends results from the inclusion of aromatic rings, which facilitate long-range tunneling (up to ca. 3 nm) between isolated CP chains. This tunneling mechanism calls into question the current paradigm used to design CPs, where the solubilizing or ionically conducting component is considered electronically inert. Indeed, optimizing the participation of the nominally insulating component in electronic transport may lead to enhanced electronic mobility and overall better performance in CPs.

    View details for DOI 10.1021/jacs.2c02139

    View details for PubMedID 35658455

  • 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

  • High-Speed Ionic Synaptic Memory Based on 2D Titanium Carbide MXene ADVANCED FUNCTIONAL MATERIALS Melianas, A., Kang, M., VahidMohammadi, A., Quill, T., Tian, W., Gogotsi, Y., Salleo, A., Hamedi, M. 2021
  • 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