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A rapidly growing interest in organic bioelectronic applications has spurred the development of a wide variety of organic mixed ionic‐electronic conductors. While these new mixed conductors have enabled the community to interface organic electronics with biological systems and efficiently transduce biological signals (ions) into electronic signals, the current materials selection does not offer sufficient selectivity towards specific ions of biological relevance without the use of auxiliary components such as ion‐selective membranes. Here, we present the molecular design of an n‐type (electron‐transporting) perylene diimide semiconductor material decorated with pendant oligoether groups to facilitate interactions with cations such as Na+ and K+. Using the cyclic 15‐crown‐5 oligoether motif, we find that the resulting mixed conductor PDI‐crown displays a strong dependence on the size of the electrolyte cation when tested in an organic electrochemical transistor configuration. In stark contrast to the low current response on the order of 1 μA observed with aqueous sodium chloride, a nearly 200‐fold increase in current is observed with aqueous potassium chloride. We ascribe the high selectivity to extended molecular aggregation and therefore efficient charge transport in the presence of K+ due to a favourable sandwich‐like structure between two adjacent 15‐crown‐5 motifs and the potassium ion. [ABSTRACT FROM AUTHOR]

Organic electrochemical transistors (OECT) have shown great potential in diverse applications; however, in many OECTs, their slow transient response has thus far limited their practical use. One reason for the slow response is the complex interplay between lateral and vertical ion transport that has so far been poorly understood. In this work, we study the impact of lateral ion transport on OECT transient response, introduce a robust pre-charging method to manipulate the slow lateral ion transport. This approach leads to quicker ion redistribution and improved switching speeds. We show the general utility of pre-charging method in enhancing the switching speeds across various material systems, characterized by both low and high ion mobilities, and across different device architectures, achieving nearly symmetric speeds for both on-switching and off-switching. Moreover, we showcase the efficacy of the pre-charging method in enabling slow OECTs to capture rapid signals in real-world applications. Our findings present a groundbreaking strategy for enhancing the response times of OECT devices and deepening our understanding of the transient mechanisms in OECT device.

A detailed investigation addressing the effects of functionalizing conjugated polymers with oligo(ethylene glycol) (EGn) sidechains on the performance and polymer‐electrolyte compatibility of electrochromic devices (ECDs) is reported. The electrochemistry for a series of donor‐acceptor copolymers having near‐infrared (NIR)‐optical absorption, where the donor fragment is 3,4‐ethylenedioxythiophene (EDOT) or an EGn functionalized bithiophene (g2T) and the acceptor fragment is diketopyrrolopyrrole (DPP) functionalized with branched alkyl or EGn sidechains, is extensively probed. ECDs are next fabricated and it is found that EGn sidechain incorporation must be finely balanced to promote polymer‐electrolyte compatibility and provide efficient ion exchange. Proper electrolyte‐cation pairing and polymer structural tuning affords a 2x increase in optical contrast (from 12% to 24%) and >60x reduction in switching time (from 20 to 0.3 s). Atomic force microscopy (AFM)/grazing incidence wide‐angle X‐ray scattering (GIWAXS) characterization of the polymer film morphology/microstructure reveals that an over‐abundance of EGn sidechains generates large polymer crystallites, which can suppress ion exchange. Lastly, time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS) indicates sidechain/electrolyte identity does not influence the electrolyte penetration depth into the films, and EGn sidechain inclusion increases electrolyte cation uptake. The material structural design insight and guidelines regarding the polymer‐electrolyte ion insertion/expulsion dynamics reported here should be of significant utility for developing next‐generation mixed ionic‐electronic conducting materials. [ABSTRACT FROM AUTHOR]

Light emission and detection are the two fundamental features of optoelectronic communication systems. Until now, both functions have been realized with a p–n diode, which is used in a wide range of applications. However, due to the competing dynamics of carrier injection and photocarrier collection, in such devices, electroluminescence and photodetection are realized separately by switching the direction of the applied electrical bias. Here, mobile ions in halide perovskites are benefited from to demonstrate electroluminescence and photodetection simultaneously, without switching the direction of the applied electrical bias. The electroluminescent photodetector consists of a CsPbBr3 microwire integrated with electrodes made of a single‐walled carbon nanotube thin film, providing Schottky barriers at the interfaces. The dual functionality stems from the modulation of these barriers by mobile ions in cooperation with photogenerated charge carriers. Furthermore, such complex charge dynamics additionally result in a novel effect: light‐enhanced electroluminescence. The new optoelectronic phenomena demonstrated in the simple lateral device design will expand the applications of mixed ionic‐electronic conductors toward cheap and efficient multifunctional optoelectronic devices able to simultaneously generate and receive optical data. [ABSTRACT FROM AUTHOR]

In the present report, the combined effects of the co-doping of metal oxide (Bi 2 O 3) and Lithium oxide (Li 2 O) into the glassy matrix with chemical composition xLi 2 O-(0.45-x)Bi 2 O 3 -(0.15ZnO-0.40P 2 O 5) (x = 0.05, 0.15, 025, and 0.35 mol%) are investigated thoroughly. The FESEM and X-ray diffraction data affirm the crystalline nature of the studied glassy composites. The obtained band gap energy values are declined from (3.68–3.17) eV, while the Urbach energy values are declined from (0.38–0.27) eV. Moreover, the mechanism responsible for AC conductivity has been analyzed using Almond–West formalism and Jonscher's universal power law. The observed rise in both AC and DC conductivity in the glass samples is attributed to the mixed ionic electronic effect. In the ionic diffusion model, an increased defect site concentration improves Li+ ion migration through percolation channels. The reduction in both electrostatic binding energy and strain energy lowers the Anderson-Stuart activation energy, facilitating Li+ ion migration and enhancing conductivity. Additionally, in the small polaron hopping model, an increase in the density of defect states suggests more defect sites that facilitate electronic hopping, creating deep localized states and transitions between localized and extended states. Replacing a Bismuth atom with a Lithium atom increases the number of non-bridging oxygen, enhancing the conduction band tail, reducing the energy needed for hopping conductivity, and increasing conductivity. [ABSTRACT FROM AUTHOR]

In view of its important role as raw materials in various energy and environment fields, pure oxygen has been widely required. The present cryogenic distillation, polymeric membrane and pressure swing adsorption (PSA) air separation methods are either energy-intensive or producing non-high purity oxygen. The comparative analysis of the inorganic dense ceramic-based oxygen transport membranes (OTMs) with these traditional oxygen production technologies and the H 2 /O 2 production by electrolysis of water shows irreplaceable advantages. The oxygen transport mechanism has been elaborated further to reveal the theoretical basis for the development of OTMs. The dual-phase membranes that have been widely studied are divided into three types according to the conduction paths of oxygen ions and electrons. Based on a review of the different types of OTM materials experienced in the past 30 years, its applications such as oxygen-enriched combustion involving H 2 and membrane reactors have been discussed. Finally, challenges and future directions are analyzed according to potential industrial design directions and competitive technologies of OTMs. • Progress of oxygen transport membrane architecture and materials is presented. • Dual-phase membrane is subdivided into three types by particle conduction paths. • Electrolytic water, membrane and traditional O 2 production ways are analyzed. • The development history and application of membrane are summarized in detail. • Membrane reactor to produce pure H 2 (>99.99%) for fuel cell is discussed. [ABSTRACT FROM AUTHOR]

Conjugated polymers with mixed ionic and electronic transport are essential for developing the complexity and function of electrochemical devices. Current n‐type materials have a narrow scope and low performance compared with their p‐type counterparts, requiring new molecular design strategies. This work presents two naphthalene diimide‐bithiophene (NDI‐T2) copolymers functionalized with hybrid alkyl‐glycol side chains, where the naphthalene diimide unit is segregated from the ethylene glycol (EG) units within the side chain by an alkyl spacer. Introduction of hydrophobic propyl and hexyl spacers is investigated as a strategy to minimize detrimental swelling close to the conjugated backbone and balance the mixed conduction properties of n‐type materials in aqueous electrolytes. It is found that both polymers functionalized with alkyl spacers outperform their analogue bearing EG‐only side chains in organic electrochemical transistors (OECTs). The presence of the alkyl spacers also leads to remarkable stability in OECTs, with no decrease in the ON current after 2 h of operation. Through this versatile side chain modification, this work provides a greater understanding of the structure‐property relationships required for n‐type OECT materials operating in aqueous media. [ABSTRACT FROM AUTHOR]

A series of semiconducting small molecules with bithiophene or bis‐3,4‐ethylenedioxythiophene cores are designed and synthesized. The molecules display stable reversible oxidation in solution and can be reversibly oxidized in the solid state with aqueous electrolyte when functionalized with polar triethylene glycol side chains. Evidence of promising ion injection properties observed with cyclic voltammetry is complemented by strong electrochromism probed by spectroelectrochemistry. Blending these molecules with high molecular weight polyethylene oxide (PEO) is found to improve both ion injection and thin film stability. The molecules and their corresponding PEO blends are investigated as active layers in organic electrochemical transistors (OECTs). For the most promising molecule:polymer blend (P4E4:PEO), p‐type accumulation mode OECTs with µA drain currents, μS peak transconductances, and a µC* figure‐of‐merit value of 0.81 F V−1 cm−1 s−1 are obtained. [ABSTRACT FROM AUTHOR]

Conjugated polymers that support mixed (electronic and ionic) conduction are in demand for applications spanning from bioelectronics to energy harvesting and storage. To design polymer mixed conductors for high‐performance electrochemical devices, relationships between the chemical structure, charge transport, and morphology must be established. A polymer series bearing the same p‐type conjugated backbone with increasing percentage of hydrophilic, ethylene glycol side chains is synthesized, and their performance in aqueous electrolyte gated organic electrochemical transistors (OECTs) is studied. By using device physics principles and electrochemical analyses, a direct relationship is found between the OECT performance and the balanced mixed conduction. While hydrophilic side chains are required to facilitate ion transport—thus enabling OECT operation—swelling of the polymer is not de facto beneficial for balancing mixed conduction. It is shown that heterogeneous water uptake disrupts the electronic conductivity of the film, leading to OECTs with lower transconductance and slower response times. The combination of in situ electrochemical and structural techniques shown here contributes to the establishment of the structure–property relations necessary to improve the performance of polymer mixed conductors and subsequently of OECTs. [ABSTRACT FROM AUTHOR]

Over the last decade, the organic electrochemical transistor (OECT) has appeared as a powerful platform for developing organic bioelectronic applications such as electronic biosensors and neuromorphic devices. The rapidly growing interest in this field has spurred the development of new active bioelectronic materials that are tailor-made to fulfil the mixed ionic-electronic conduction requirements of the OECT. While p-type (hole-transporting) organic semiconductors quickly appeared with impressive mixed conduction properties, their electron-transporting counterparts, n-type organic semiconductors have lagged severely in terms of OECT performance metrics. Here, we review recent progress on the development of n-type organic semiconductors, including both small-molecule and polymer systems, for OECT applications and discuss the bioelectronic applications that have emerged from the materials development. • Over the last couple of years, n-type semiconductors have progressed significantly in the context of mixed ionic-electronic conduction. • We review the recent literature on n-type semiconductors for bioelectronic applications covering both small-molecule and polymer systems and their OECT performance. • We give an overview of noteworthy applications that utilise these new materials and their specific properties and discuss the challenges and future directions of the field. [ABSTRACT FROM AUTHOR]

Oxygen permeation measurements are performed on dense samples of CaTi 0.85 Fe 0.15 O 3− δ , CaTi 0.75 Fe 0.15 Mg 0.05 O 3− δ and CaTi 0.75 Fe 0.15 Mn 0.10 O 3− δ in combination with density functional theory (DFT) calculations and X-ray photoelectron spectroscopy (XPS) in order to assess Mg and Mn as dopants for improving the O 2 permeability of CaTi 1− x Fe x O 3− δ based oxygen separation membranes. The oxygen permeation measurements were carried out at temperatures ranging between 700 and 1000 °C with feed side oxygen partial pressures between 0.01 and 1 bar. The O 2 permeability was experimentally found to be highest for the Mn doped sample over the whole temperature range, reaching 4.2×10 −3 ml min −1 cm −1 at 900 °C and 0.21 bar O 2 in the feed which corresponds to a 40% increase over the Fe-doped sample and similar to reported values for x =0.2. While the O 2 permeability of the Mg doped sample was also higher than the Fe-doped sample, it approached that of the Fe-doped sample above 900 °C. According to the DFT calculations, Mn introduces electronic states within the band gap and will predominately exist in the effectively negative charge state, as indicated by XPS measurements. Mn may therefore improve the ionic and electronic conductivity of CTF based membranes. The results are discussed in terms of the limiting species for ambipolar transport and O 2 permeability, i.e., oxygen vacancies and electronic charge carriers. [ABSTRACT FROM AUTHOR]

Abstract: Although Nernst observed ionic conduction of zirconia–yttria solutions in 1899, the field of oxygen separation research remained dormant. In the last 30 years, research efforts by the scientific community intensified significantly, stemming from the pioneering work of Takahashi and co-workers, with the initial development of mixed ionic–electronic conducting (MIEC) oxides. A large number of MIEC compounds have been synthesized and characterized since then, mainly based on perovskites (ABO3−δ and A2BO4±δ ) and fluorites (A δ B1−δ O2−δ and A2δ B2−2δ O3), or dual-phases by the introduction of metal or ceramic elements. These compounds form dense ceramic membranes, which exhibit significant oxygen ionic and electronic conductivity at elevated temperatures. In turn, this process allows for the ionic transport of oxygen from air due to the differential partial pressure of oxygen across the membrane, providing the driving force for oxygen ion transport. As a result, defect-free synthesized membranes deliver 100% pure oxygen. Electrons involved in the electrochemical oxidation and reduction of oxygen ions and oxygen molecules respectively are transported in the opposite direction, thus ensuring overall electrical neutrality. Notably, the fundamental application of the defect theory was deduced to a plethora of MIEC materials over the last 30 years, providing the understanding of electronic and ionic transport, in particular when dopants are introduced to the compound of interest. As a consequence, there are many special cases of ionic oxygen transport limitation accompanied by phase changes, depending upon the temperature and oxygen partial pressure operating conditions. This paper aims at reviewing all the significant and relevant contribution of the research community in this area in the last three decades in conjunction with theoretical principles. [Copyright &y& Elsevier]

CO 2 uphill permeation is interpreted as being in accordance with the recently developed permeation model. The model allows the conditions to be qualified for the occurrence of the phenomenon. [ABSTRACT FROM AUTHOR]

Coupled electron/ion transport is a defining characteristic of electrochemical processes, for example, battery charge/discharge. Analytical models that represent the complex transport and electrochemical processes in an electrode in terms of equivalent electrical circuits provide a simple, but successful framework for understanding the kinetics of these coupled transport phenomena. The premise of this review is that the nature of the time-dependent phase transitions in dynamic electrochemical environments serves as an important design parameter, orthogonal to the intrinsic mixed conducting properties of the active materials in battery electrodes. A growing body of literature suggests that such phase transitions can produce divergent extrinsic resistances in a circuit model ( e . g ., R e , describing electron transport from an active electrode material to the current collector of an electrode, and/or R ion , describing ion transport from a bulk electrolyte to the active material surface). It is found that extrinsic resistances of this type play a determinant role in both the electrochemical performance and long-term stability of most battery electrodes. Additionally, successful suppression of the tendency of extrinsic resistances to accumulate over time is a requirement for practical rechargeable batteries and an important target for rational design. We highlight the need for battery electrode and cell designs, which explicitly address the specific nature of the structural phase transition in active materials, and for advanced fabrication techniques that enable precise manipulations of matter at multiple length scales: (i) meso-to-macroscopic conductive frameworks that provide contiguous electronic/ion pathways; (ii) nanoscale uniform interphases formed on active materials; and (iii) molecular-level structures that promote fast electron and/or ion conduction and mechanical resilience.

This review aims to give more understanding of the selection and development of oxygen carrier materials for chemical looping. Chemical looping, a rising star in chemical technologies, is capable of low CO2 emissions with applications in the production of energy and chemicals. A key issue in the further development of chemical looping processes and its introduction to the industry is the selection and further development of an appropriate oxygen carrier (OC) material. This solid oxygen carrier material supplies the stoichiometric oxygen needed for the various chemical processes. Its reactivity, cost, toxicity, thermal stability, attrition resistance, and chemical stability are critical selection criteria for developing suitable oxygen carrier materials. To develop oxygen carriers with optimal properties and long-term stability, one must consider the employed reactor configuration and the aim of the chemical looping process, as well as the thermodynamic properties of the active phases, their interaction with the used support material, long-term stability, internal ionic migration, and the advantages and limits of the employed synthesis methods. This review, therefore, aims to give more understanding into all aforementioned aspects to facilitate further research and development of chemical looping technology. [ABSTRACT FROM AUTHOR]

A series of glycolated polythiophenes for use in organic electrochemical transistors (OECTs) is designed and synthesized, differing in the distribution of their ethylene glycol chains that are tethered to the conjugated backbone. While side chain redistribution does not have a significant impact on the optoelectronic properties of the polymers, this molecular engineering strategy strongly impacts the water uptake achieved in the polymers. By careful optimization of the water uptake in the polymer films, OECTs with unprecedented steady-state performances in terms of [μC * ] and current retentions up to 98% over 700 electrochemical switching cycles are developed., (© 2020 The Authors. Published by Wiley-VCH GmbH.)