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Transparent electrodes (TEs) are vital in optoelectronic devices, enabling the interaction of light and charges. While indium tin oxide (ITO) has traditionally served as a benchmark TE, its high cost prompts the exploration of alternatives to optimize electrode characteristics and improve device efficiencies. Conducting polymers, which combine polymer advantages with metal‐like conductivity, emerge as a promising solution for TEs. This work introduces a two‐in‐one electron transport layer (ETL) and TE based on films of polyethylenimine ethoxylated (PEIE)‐modified poly(benzodifurandione) (PBFDO). These PEIE‐modified PBFDO layers exhibit a unique combination of properties, including low sheet resistance (130 Ω sq−1), low work function (4.2 eV), and high optical transparency (>85% in the UV–vis‐NIR range). In contrast to commonly used poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS), the doping level of PBFDO remains unaffected by the PEIE treatment, as verified through UV–vis‐NIR absorption and X‐ray photoelectron spectroscopy measurements. When employed as a two‐in‐one ETL/TE in organic solar cells, the PEIE‐modified PBFDO electrode exhibits performance comparable to conventional ITO electrodes. Moreover, this work demonstrates all‐organic solar cells with record‐high power conversion efficiencies of >15.1% under indoor lighting conditions. These findings hold promise for the development of fully printed, all‐organic optoelectronic devices. [ABSTRACT FROM AUTHOR]

Thermoelectric textile devices represent an intriguing avenue for powering wearable electronics. The lack of air‐stable n‐type polymers has, until now, prevented the development of n‐type multifilament yarns, which are needed for textile manufacturing. Here, the thermomechanical properties of the recently reported n‐type polymer poly(benzodifurandione) (PBFDO) are explored and its suitability as a yarn coating material is assessed. The outstanding robustness of the polymer facilitates the coating of silk yarn that, as a result, displays an effective bulk conductivity of 13 S cm−1, with a projected half‐life of 3.2 ± 0.7 years at ambient conditions. Moreover, the n‐type PBFDO coated silk yarn with a Young's modulus of E = 0.6 GPa and a strain at break of εbreak = 14% can be machine washed, with only a threefold decrease in conductivity after seven washing cycles. PBFDO and poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) coated silk yarns are used to fabricate two out‐of‐plane thermoelectric textile devices: a thermoelectric button and a larger thermopile with 16 legs. Excellent air stability is paired with an open‐circuit voltage of 17 mV and a maximum output power of 0.67 µW for a temperature difference of 70 K. Evidently, PBFDO coated multifilament silk yarn is a promising component for the realization of air stable thermoelectric textile devices. [ABSTRACT FROM AUTHOR]

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]

A new approach to control the n‐doping reaction of organic semiconductors is reported using surface‐functionalized gold nanoparticles (f‐AuNPs) with alkylthiols acting as the catalyst only upon mild thermal activation. To demonstrate the versatility of this methodology, the reaction of the n‐type dopant precursor N‐DMBI‐H with several molecular and polymeric semiconductors at different temperatures with/without f‐AuNPs, vis‐à‐vis the unfunctionalized catalyst AuNPs, was investigated by spectroscopic, morphological, charge transport, and kinetic measurements as well as, computationally, the thermodynamic of catalyst activation. The combined experimental and theoretical data demonstrate that while f‐AuNPs is inactive at room temperature both in solution and in the solid state, catalyst activation occurs rapidly at mild temperatures (~70 °C) and the doping reaction completes in few seconds affording large electrical conductivities (~10–140 S cm−1). The implementation of this methodology enables the use of semiconductor+dopant+catalyst solutions and will broaden the use of the corresponding n‐doped films in opto‐electronic devices such as thin‐film transistors, electrochemical transistors, solar cells, and thermoelectrics well as guide the design of new catalysts. [ABSTRACT FROM AUTHOR]

The surge in the number of distributed microelectronics and sensors requires versatile, scalable, and affordable power sources. Heat‐harvesting organic thermoelectric generators (TEGs) are regarded as potential key components of the future energy landscape. Recent advances in the performance of organic thermoelectric materials have made practical applications of organic TEGs more feasible than ever before, yet the challenges of designing and fabricating organic TEGs suitable for real scenarios are scarcely addressed. Specifically, small sensors and wearables demand for micro‐thermoelectric generators (µTEGs) with high power density architectures and small form factors, while typical demonstrations of organic TEGs are characterized by < 10 thermocouples (TCs) per cm2. This work presents a rolled, organic µTEG architecture combining large‐area, solution‐based deposition techniques, such as inkjet and spray‐coating, and an ultrathin parylene substrate to achieve a thermocouple density of 1842 TCs cm−2. Such demonstrative µTEG reaches a thermoelectric conversion performance of 0.15 µW cm−2 at ΔT = 50 K. Such power output is well in line with finite element method simulations, which highlight the benefit of the architecture and show that remarkable power densities, in the mW cm−2 range at ΔT = 10 K, are realistically achievable with geometrical improvements and already ongoing advancements in organic thermoelectric inks. [ABSTRACT FROM AUTHOR]

Organic semiconductors are increasingly being decorated with hydrophilic solubilising chains to create materials that can function as mixed ionic–electronic conductors, which are promising candidates for interfacing biological systems with organic electronics. While numerous organic semiconductors, including p- and n-type materials, small molecules and polymers, have been successfully tailored to encompass mixed conduction properties, common to all these systems is that they have been semicrystalline materials. Here, we explore how side chain engineering in the nano-crystalline indacenodithiophene-co-benzothiadiazole (IDTBT) polymer can be used to instil ionic transport properties and how this in turn influences the electronic transport properties. This allows us to ultimately assess the mixed ionic–electronic transport properties of these new IDTBT polymers using the organic electrochemical transistor as the testing platform. Using a complementary experimental and computational approach, we find that polar IDTBT derivatives can be infiltrated by water and solvated ions, they can be electrochemically doped efficiently in aqueous electrolyte with fast doping kinetics, and upon aqueous swelling there is no deterioration of the close interchain contacts that are vital for efficient charge transport in the IDTBT system. Despite these promising attributes, mixed ionic–electronic charge transport properties are surprisingly poor in all the polar IDTBT derivatives. Albeit a "negative" result, this finding clearly contradicts established side chain engineering rules for mixed ionic–electronic conductors, which motivated our continued investigation of this system. We eventually find this anomalous behaviour to be caused by increasing energetic disorder in the polymers with increasing polar side chain content. We have investigated computationally how the polar side chain motifs contribute to this detrimental energetic inhomogeneity and ultimately use the learnings to propose new molecular design criteria for side chains that can facilitate ion transport without impeding electronic transport. [ABSTRACT FROM AUTHOR]

Ice formation detection is important in telecommunications and aeronautics, e.g., ice on the wings of an aircraft affects its aerodynamic performance and leads to fatal accidents. While many types of sensors exist, resistive sensors for ice detection have been poorly explored. They are however attractive because of their simplicity and the possibility to install an array of sensors on large areas to map the ice formation on wings. Hygroscopic ionic conductors have been demonstrated for resistive ice sensing but their high resistance prevents the readout of sensor arrays. In this work, mixed ionic‐electronic polymer conductors (MIEC) are considered for the first time for ice detection. The polymer blend poly(3,4‐ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) is solution deposited on a pair of electrodes. The sensor displays an abrupt rise in electrical resistance during the transition phase between water liquid to solid. It is proposed that the morphology and electronic transport in PEDOT are affected by the freezing event because the absorbed water in the PSS‐rich phase undergoes dilatation upon forming ice crystals. For the aeronautics application, successful tests of integration of sensing layer in pre‐preg layers of aeronautical grade and freezing detection are carried out to validate the ice detection principle. [ABSTRACT FROM AUTHOR]

The first Telluride Science meeting (formerly TSRC) on organic mixed ionic and electronic conductors (OMIECs), Oct 3–7, 2022, brought together researchers across the field to understand the fundamental processes and identify out-standing questions related to this exciting class of materials. OMIECs are organic materials that promote the transport of mobile electronic charge carriers while simultaneously supporting ionic transport and ionic–electronic coupling. These properties open up broad areas of applications from energy to bioelectronics. Devices include batteries, supercapacitors, actuators, electrochromic displays, and organic electrochemical transistors (OECTs). They possess the key strengths of traditional organic electronic materials, such as synthetic tunability and low-temperature processing. Despite the recent advances in devices and applications achieved with such materials, many challenges and gaps in understanding remain. These topics hold the key to designing next-generation materials and devices that continue to push the limits of performance and stability and facilitate novel functionality. This perspective aims to summarize the current understanding, conversations, and debates that made this TSRC particularly engaging, enabling new directions and searching for missing pieces of the OMIEC puzzle. [ABSTRACT FROM AUTHOR]

Operational stability is essential for the success of organic electrochemical transistors (OECTs) in bioelectronics. The oxygen reduction reaction (ORR) is a common electrochemical side reaction that can compromise the stability of OECTs, but the relationship between ORR and materials degradation is poorly understood. In this study, the impact of ORR on the stability and degradation mechanisms of thiophene‐based OECTs is investigated. The findings show that an increase in pH during ORR leads to the degradation of the polymer backbone. By using a protective polymer glue layer between the semiconductor channel and the aqueous electrolyte, ORR is effectively suppressed and the stability of the OECTs is significantly improved, resulting in current retention of nearly 90% for ≈2 h cycling in the saturation regime. [ABSTRACT FROM AUTHOR]

Future brain–computer interfaces will require local and highly individualized signal processing of fully integrated electronic circuits within the nervous system and other living tissue. New devices will need to be developed that can receive data from a sensor array, process these data into meaningful information, and translate that information into a format that can be interpreted by living systems. Here, the first example of interfacing a hardware‐based pattern classifier with a biological nerve is reported. The classifier implements the Widrow–Hoff learning algorithm on an array of evolvable organic electrochemical transistors (EOECTs). The EOECTs' channel conductance is modulated in situ by electropolymerizing the semiconductor material within the channel, allowing for low voltage operation, high reproducibility, and an improvement in state retention by two orders of magnitude over state‐of‐the‐art OECT devices. The organic classifier is interfaced with a biological nerve using an organic electrochemical spiking neuron to translate the classifier's output to a simulated action potential. The latter is then used to stimulate muscle contraction selectively based on the input pattern, thus paving the way for the development of adaptive neural interfaces for closed‐loop therapeutic systems. [ABSTRACT FROM AUTHOR]

A conjugated‐polymer‐based n‐type yarn for thermoelectric textiles is presented. Thermoelectric textile devices are intriguing power sources for wearable electronic devices. The use of yarns comprising conjugated polymers is desirable because of their potentially superior mechanical properties compared to other thermoelectric materials. While several examples of p‐type conducting yarns exist, there is a lack of polymer‐based n‐type yarns. Here, a regenerated cellulose yarn is spray‐coated with an n‐type conducting‐polymer‐based ink composed of poly(benzimidazobenzophenanthroline) (BBL) and poly(ethyleneimine) (PEI). The n‐type yarns display a bulk electrical conductivity of 8 × 10−3 S cm−1 and Seebeck coefficient of −79 µV K−1. A promising level of air‐stability for at least 13 days can be achieved by applying an additional thermoplastic elastomer coating. A prototype in‐plane thermoelectric textile, produced with the developed n‐type yarns and p‐type yarns, composed of poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS)‐coated regenerated cellulose, displays a stable device performance in air for at least 4 days with an open‐circuit voltage per temperature difference of 1 mV °C−1. Evidently, polymer‐based n‐type yarns are a viable component for the construction of thermoelectric textile devices. [ABSTRACT FROM AUTHOR]

n‐Type semiconducting polymers with high thermoelectric performance remain challenging due to the scarcity of molecular design strategy, limiting their applications in organic thermoelectric (OTE) devices. Herein, we provide a new approach to enhance the OTE performance of n‐doped polymers by introducing acceptor‐acceptor (A‐A) type backbone bearing branched ethylene glycol (EG) side chains. When doped with 4‐(2,3‐dihydro‐1,3‐dimethyl‐1H‐benzimidazol‐2‐yl)‐N,N‐dimethylbenzenamine (N‐DMBI), the A‐A homopolymer PDTzTI‐TEG exhibits n‐type electrical conductivity (σ) up to 34 S cm−1 and power factor value of 15.7 μW m−1 K−2. The OTE performance of PDTzTI‐TEG is far greater than that of homopolymer PBTI‐TEG (σ=0.27 S cm−1), indicating that introducing electron‐deficient thiazole units in the backbone further improves the n‐doping efficiency. These results demonstrate that developing A‐A type polymers with EG side chains is an effective strategy to enhance n‐type OTE performance. [ABSTRACT FROM AUTHOR]

Introduction of filler materials into organic solar cells (OSCs) are a promising strategy to improve device performance and thermal/mechanical stability. However, the complex interactions between the state‐of‐the‐art OSC materials and filler require careful selection of filler materials and OSC fabrication to achieve lower cost and improved performance. In this work, the introduction of a natural product betulin‐based insulating polymer as filler in various OSCs is investigated. Donor–acceptor–insulator ternary OSCs are developed with improved open‐circuit voltage (Voc) due to decreased trap‐assisted recombination. Furthermore, filler‐induced vertical phase separation due to mismatched surface energy can strongly affect charge collection at the bottom interface and limit the filler ratio. A quasi‐bilayer strategy is used in all‐polymer systems to circumvent this problem. Herein, the variety of filler materials in OSCs to biomass is broadened, and the filler strategy is made a feasible and promising strategy toward highly efficient, eco, and low‐cost OSCs. [ABSTRACT FROM AUTHOR]

The article offers information on the development of semiconducting hydrogels for use in bioelectronic interfaces, focusing on recent advances in materials science. Topics include the challenges of using rigid electronics in bioelectronic applications; the properties of hydrogels that make them suitable for biocompatible interfaces; and the synthesis of an electron-transporting polymer for creating semiconducting hydrogels.