Bulletin of the American Physical Society
APS March Meeting 2022
Volume 67, Number 3
Monday–Friday, March 14–18, 2022; Chicago
Session M16: Organic Electronics I: Mixed Transport in Conjugated and Open-Shell PolymersFocus Recordings Available
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Sponsoring Units: DPOLY Chair: Rafael Verduco, Rice University Room: McCormick Place W-184A |
Wednesday, March 16, 2022 8:00AM - 8:36AM |
M16.00001: Mixed Charge Transport in Conjugated Polymers and its Impact on Biosensor Performance Invited Speaker: Sahika Inal Organic mixed conductors and electrochemical phenomena at solid-liquid interfaces have garnered significant attention for applications in bioelectronics, electrochromics, energy storage/conversion, neuromorphic computing, and thermoelectrics. These devices operate in electrolytes that render ions mobile in the film, making the coupling between electronic and ionic charges crucial. A prime example of such devices is the organic electrochemical transistor (OECT), a transducer used commonly to monitor bioelectronic signals. In this talk, I will introduce the class of conjugated polymers that have been used in OECT channels and methods to benchmark their performance. In operando techniques reveal that the ions enter the polymeric channel hydrated and that the excess swelling of the material has a significant imapct on device characteristics, which can be traced back to changes in the overall structural order. I will then introduce OECT based platforms for pathogen detection and discuss how their performance is affected by the type of mixed conductors used in the channel. Our work highlights the importance of characterizing the properties of conjugated polymer films n their electrolyte swollen state for drawing conclusions related to materials properties/device performance, which has a tremendous impact on the performance of biosensors. |
Wednesday, March 16, 2022 8:36AM - 8:48AM |
M16.00002: Understanding the Transient Behavior of Organic Electrochemical Transistors Pushpa R Paudel, Michael A Skowrons, Drona Dahal, Chathuranga Prageeth H Rajapaksha, Raj Kishen R Krishnan, Antal I Jakli, Bjorn Lussem Their ability to operate at low voltages and in aqueous media makes Organic Electrochemical Transistors (OECT) highly promising for bio-electronic applications. Their maximum switching frequency is a deciding factor for some of the applications targeted by OECTs. A thorough understanding of the transient behavior of OECTs and a detailed formulation of design rules for high speed OECTs are therefore essential for a widespread application of this technology. |
Wednesday, March 16, 2022 8:48AM - 9:00AM |
M16.00003: Radical Polymer-based Organic Electrochemical Transistors Ho Joong Kim, Kuluni Perera, Zihao Liang, Jianguo Mei, Bryan W Boudouris The well-established design rules for organic electrochemical transistor (OECT) materials utilize various conjugated backbones with hydrophilic side chains to allow mixed electronic and ionic conduction to occur. To further our understanding of the underlying structure-property relations of OECT active layer materials, we design an OECT which incorporates a nonconjugated radical polymer in the active layer. Specifically, poly(4-glycidyloxy-2,2,6,6-tetramethylpiperidine-1-oxyl) (PTEO) is blended with an oft-used conjugated polymer, poly(3-hexylthiophene) (P3HT), to create films with distinct closed-shell and open-shell domains. The well-defined oxidation-reduction (redox) potential associated with the radical moieties of the PTEO provides a sharp actuation feature that modulates the ionic transport and regulates doping of the P3HT phase within the blended film. Electrochemical analysis reveals that the blending strategy also improves packing within each domain. The present design strategy leads to figure-of-merit (i.e., µC*) values > 150 F V−1 cm−1 s−1 at loadings as low as 5% PTEO (by weight), which is never-before-seen performance for a P3HT-based OECT. As such, this effort presents a design platform by which to readily create tailored OECT response through strategic macromolecular selection and polymer processing. |
Wednesday, March 16, 2022 9:00AM - 9:12AM |
M16.00004: Sensitive and Specific Virus and Protein Detection using Organic Electrochemical Transistors Yilin Li, Ying Zhou, Casper Huang, Pedro Alvarez, Yizhi Tao, Rafael Verduzco There is a need for low-cost, fast, and sensitive sensors for the detection of viruses and proteins. Recent work has shown that organic electrochemical transistors (OECTs) can be used as highly sensitive and specific sensors for biological activity, electrochemical reactions, viruses, and biomolecules. Here, we demonstrate a general approach to the detection of SARS-CoV-2 spike protein and virus using OECTs functionalized with engineered proteins. The devices can be fabricated quickly without microfabrication techniques, and a specific response is achieved by immobilizing a protein engineered to bind to the SARS-CoV-2 spike protein on the OECT channel. Binding of SARS-CoV-2 spike protein or virus to the channel produces a significant shift in the transfer curve, and through analysis of the normalized current we determined a sensitivity as low as 10-18 M for detection of SARS-CoV-2 spike protein and 40 pfu/mL for SARS-CoV-2 virus. The devices are non-responsive to other proteins or viruses, including influenza A, SARS-CoV-2, and OC43. This work demonstrates that OECTs are effective devices for rapid, sensitive, and specific detection of target viruses. |
Wednesday, March 16, 2022 9:12AM - 9:24AM |
M16.00005: Understanding the role of electrode composition on the current-voltage response of Cu/PEDOT: PSS/ITO memristive device. Subhadeep Koner, Stephen A Sarles Resistive switching devices with metal/PEDOT:PSS thin film/metal sandwich configuration, display pinched hysteretic current-voltage (i-v) response to periodic voltage input, a signature of memristors. Several studies have focused on revealing the switching mechanism using symmetric electrode materials like Gold (Au) or Aluminum (Al). Realizing the influence of asymmetric electrode composition on the i-v response of PEDOT:PSS, using copper (Cu) as an electrode material is currently missing. Therefore, our objective is to study the role of Cu on the memristive i-v response of Cu/PEDOT:PSS/ Indium Tin Oxide (ITO) devices. |
Wednesday, March 16, 2022 9:24AM - 10:00AM |
M16.00006: To Pattern or Not to Pattern? Selecting Side-Chains for Mixed Conducting Polymers Invited Speaker: Brett M Savoie Organic mixed ionic-electronic conductors (OMIECs) are a developing class of organic electronic materials distinguished by their dual modes of conduction. The side-chains of OMIEC polymers are responsible for forming a percolating electrolyte phase that mediates doping and ionic conduction. Despite this critical role, design rules for OMIEC side-chains are still nascent and their effects on OMIEC morphology and charge transport have yet to be systematically studied. In this presentation, I will describe our recent development of coarse-grained model of mixed conductors that can be used to study the relationships between OMIEC morphology, charge transport, and ion transport. Using this methodology, we have performed the first systematic study of the impact of introducing side chains of varying hydrophilicity and pattern into the OMIEC backbone. I will highlight the structure-function relationships that have been established to date through several illustrative case studies, and also discuss where opportunities exist for side-chain engineering. |
Wednesday, March 16, 2022 10:00AM - 10:12AM |
M16.00007: Revealing the Intricate Optical Spectra of Organic Open-Shell Conjugated Polymers Neeraj Rai, Chandra S Sarap, Yashpal Singh Organic semiconductors based on conjugated donor-acceptor (D-A) polymers are a unique platform for electronics devices, spintronics, and energy harvesting opportunities. Developing a better understanding of the electronic structure of D-A polymers, especially with high-spin states, is necessary to create next-generation technologies. Herein, we investigate the optoelectronic properties of open-shell D-A polymers using density functional theory (DFT) and advanced computational methods such as GW approximation and Bethe-Salpeter equation (BSE). Using the spin-polarized method, including spin-orbit coupling (SOC), we demonstrate the open/close-shell, strong electron correlation, narrow bandgap, and dielectric properties. The electron occupancy in the valence band (VB) and conduction band (CB) and repositioning of electrons from the VB to CB along different wave vectors reveals localized spins in the polymer backbone articulating multiradical character. The optical spectra computed using the BSE approach accurately predict the exciton peak and agree with the polymers' experimental optical gap. |
Wednesday, March 16, 2022 10:12AM - 10:24AM |
M16.00008: Predicting Molecular Charge Transport in Radical Polymers Ying Tan, Bryan W Boudouris, Brett M Savoie Nonconjugated macromolecules bearing stable radical pendent groups (i.e., radical polymers) exhibit unique redox and optoelectronic attributes compared with conventional doped conjugated polymers. However, critical questions remain on ultimate limits of charge transport in these materials and whether some of the deficiencies exhibited by contemporary materials are due to the choice of radical chemistry. To address these questions, density functional theory was used to evaluate the charge transfer characteristics of a broad range of pairwise open-shell chemistries relevant to radical conductors, including p-type (i.e., hole-transporting), n-type (i.e., electron-transporting), and ambipolar species based on Marcus theory. We have observed an apparent mismatch between the configurations that are energetically favorable and those that maximize charge transfer, and the configurational averaging for these quantities could vary by several orders of magnitude. These results highlight the significance of modular design approaches for fine-tuning the radical orientation to promote charge transport in radical polymers. |
Wednesday, March 16, 2022 10:24AM - 10:36AM |
M16.00009: Predicting Electronic Properties of Radical Polymers at Coarse-Grained Resolutions Riccardo Alessandri, Juan De Pablo Radical polymers are conducting polymers comprised of non-conjugated backbones and radical-containing side chains. Radical polymers are promising materials for applications in all-organic energy or memory storage devices. A fundamental understanding of how the chemical structure impacts charge transport in these materials is still lacking. To address this, computational approaches encompassing both mesoscale morphological features and electronic properties are required. |
Wednesday, March 16, 2022 10:36AM - 10:48AM |
M16.00010: Structure-Magnetic Property Relationships in Radical Polymers Siddhartha Akkiraju, Bryan W Boudouris Interest in open-shell polymers capable of magnetic interactions has increased in recent years due to fundamental and applied efforts. Specifically, radical polymers present new opportunities as a novel class of macromolecules with a high number of open-shell groups along a single polymer chain. To this end, the magnetic behavior of poly(4-glycidyloxy-2,2,6,6-tetramethylpiperidine-1-oxyl) (PTEO) and its precursor materials, 4-hydroxy-2,2,6,6-tetramethylpiperidin-N-oxy (TEMPO-OH) and 4-glycidyloxy-2,2,6,6-tetramethylpiperidine-1-oxyl (TEO), were quantified. Magnetic susceptibility (Xm) measurements highlighted that TEMPO-OH, TEO, and PTEO had a Xm of 1.8×10-2, 4.6×10-2, and 1.3×10-1 emu mol-1, respectively at T = 2 K. Furthermore, all three materials showed antiferromagnetic interactions between the spins. Due to its amorphous nature, PTEO had weak antiferromagnetic interactions. However, thin films of PTEO doped with TEMPO-OH showed increased antiferromagnetic interactions between the open-shell sites. In this way, this effort elucidates the magnetic structure-property relationship of radical polymers. |
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