Hole-limited electrochemical doping in conjugated polymers

Abstract

Simultaneous transport and coupling of ionic and electronic charges is fundamental to electrochemical devices used in energy storage and conversion, neuromorphic computing and bioelectronics. While the mixed conductors enabling these technologies are widely used, the dynamic relationship between ionic and electronic transport is generally poorly understood, hindering the rational design of new materials. In semiconducting electrodes, electrochemical doping is assumed to be limited by motion of ions due to their large mass compared to electrons and/or holes. Here, we show that this basic assumption does not hold for conjugated polymer electrodes. Using operando optical microscopy, we reveal that electrochemical doping speeds in a state-of-the-art polythiophene can be limited by poor hole transport at low doping levels, leading to substantially slower switching speeds than expected. We show that the timescale of hole-limited doping can be controlled by the degree of microstructural heterogeneity, enabling the design of conjugated polymers with improved electrochemical performance.

Surface Functionalization with (3-Glycidyloxypropyl)trimethoxysilane (GOPS) as an Alternative to Blending for Enhancing the Aqueous Stability and Electronic Performance of PEDOT:PSS Thin Films

“…As shown in Figure e, C scaled linearly with the film volume of varying geometries, and C * was extracted from the slope of the curve, yielding a value of 109 ± 5 F cm –3 for P@GOPS, which was about three times higher than P:GOPS (30 ± 1 F cm –3 , Figure f). Since the origin of the volumetric capacitance of PEDOT:PSS is linked to the displacement of holes by cations, the capacitance is correlated with the charge carrier concentration. , The hole densities can thus be estimated as the amount of charge stored per unit volume, at a potential where the volumetric capacitance of PEDOT:PSS is approximately constant, in an approach previously used by Salleo and co-workers (eq S4). Using the potential difference between the direct current potential from EIS measurements ( E dc , 0 V vs Ag/AgCl) and the oxidation onset of PEDOT:PSS (∼−0.9 V vs Ag/AgCl), the estimated hole density of P@GOPS (6.1 × 10 20 cm –3 ) was found to be about three times higher than the hole density of P:GOPS (1.9 × 10 20 cm –3 ).…”

Mimicking Bidirectional Inhibitory Synapse Using a Porous‐Confined Ionic Memristor with Electrolyte/Tris(4‐aminophenyl)amine Neurotransmitter

“…ii) When a forward bias or pulse is applied to the top electrode, the anions and cations in the electrolyte migrate directionally, with the anions converging toward the top Au electrode and the cations being doped into the porous CMPs layer. Due to binding with the CMPs layer, short term return of migrated ions to the solid electrolyte becomes challenging, [ 39 ] resulting in a decrease in freely mobile ions within the system. The limited increase in conductivity of the insulating CMPs due to doping leads to a continuous decline in conductivity that is hindered by synaptic weights reduction.…”

Metal-free photocatalysts for solar-driven water disinfection: recent progress and challenges

“…In recent years, conjugated polymers (CPs) have a good application prospect due to the advantages of designable band structure and molecular skeleton, and good photothermal stability. 106,107 Among them, conjugated microporous polymers (CMPs) with their unique microporous structure and photoactive π-conjugated backbone have been widely studied since they were first reported in 2007. 108,109 For instance, Zhang's group reported a series of photoactive CMP nanoparticles by adding different proportions of benzothiazole (BT) with the electrondonating thiophene (Th) unit as the polymer skeleton for bacterial inactivation in the presence of visible light (Fig.…”