Conducting polymers, particularly those capable of transporting both ionic and electronic charges-commonly referred to as organic mixed ionic-electronic conductors (OMIECs)-have played a transformative role in enabling bidirectional communication between biological systems and electronic circuits. This ability has driven the field of bioelectronics to expand in three distinct directions: biointerfacing, sensing, and neuromorphic computing. Biointerfacing and sensing allow for the extraction of interpretable chemical and electrochemical signals from living organisms, while neuromorphic computing, in addition to efficiently processing complex signals, can translate electronic signals into the frequency domain that the nervous system uses to communicate. In the bioelectronics context, OMIECs have been untethered from previous requirements of high charge mobility, fast switching times, and long-range crystallinity, which makes electropolymerization a more attractive route to fabricate OMIECs on bioelectronic devices. This review examines the fundamental principles, practical aspects, and prominent applications of OMIEC materials fabricated by electropolymerization.

Organic electrochemical transistors (OECTs) are crucial for next-generation (bio-)electronic devices but are often constrained by the use of aqueous electrolytes, which introduce crosstalk, hinder miniaturization, and limit circuit integration. Here, a photo-patternable solid-state electrolyte based on iota-carrageenan (iota-CGN) and poly(ethylene glycol) diacrylate (PEGDA) is presented, enabling high-performance OECTs and complementary circuits. The iota-CGN electrolyte exhibits high ionic conductivity (>10 mS cm(-1)), comparable to a 0.1 m NaCl aqueous electrolyte, while supporting precise patterning down to 15 mu m, fast transient response times, minimal hysteresis, and excellent stability in both p- and n-type OECTs. Compact solid-state NAND/NOR gates (500 x 800 mu m(2)), 4-input NAND gates (1600 x 800 mu m(2), 8 OECTs), and half-adders (2 x 1 mm(2), 18 OECTs) are demonstrated, all exhibiting correct logic functions and low-voltage operation. To highlight its potential for implantable bioelectronics, solid-state spiking circuits, monolithically integrated with flexible cuff electrodes, are developed for vagus nerve stimulation in mice. These findings establish iota-CGN-based solid-state electrolytes as a promising platform for scalable, implantable circuits, paving the way for next-generation bioelectronic devices.

Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) is a benchmark hole-transporting (p-type) polymer that finds applications in diverse electronic devices. Most of its success is due to its facile synthesis in water, exceptional processability from aqueous solutions, and outstanding electrical performance in ambient. Applications in fields like (opto-)electronics, bioelectronics, and energy harvesting/storage devices often necessitate the complementary use of both p-type and n-type (electron-transporting) materials. However, the availability of n-type materials amenable to water-based polymerization and processing remains limited. Herein, we present a novel synthesis method enabling direct polymerization in water, yielding a highly conductive, water-processable n-type conjugated polymer, namely, poly[(2,2 '-(2,5-dihydroxy-1,4-phenylene)diacetic acid)-stat-3,7-dihydrobenzo[1,2-b:4,5-b ']difuran-2,6-dione] (PDADF), with remarkable electrical conductivity as high as 66 S cm(-1), ranking among the highest for n-type polymers processed using green solvents. The new n-type polymer PDADF also exhibits outstanding stability, maintaining 90% of its initial conductivity after 146 days of storage in air. Our synthetic approach, along with the novel polymer it yields, promises significant advancements for the sustainable development of organic electronic materials and devices.

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 (mu TEGs) with high power density architectures and small form factors, while typical demonstrations of organic TEGs are characterized by < 10 thermocouples (TCs) per cm(2). This work presents a rolled, organic mu TEG 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 mu TEG reaches a thermoelectric conversion performance of 0.15 mu W cm(-2) at Delta T = 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 Delta T = 10 K, are realistically achievable with geometrical improvements and already ongoing advancements in organic thermoelectric inks.

Heat is an inexhaustible source of energy, and it can be exploited by thermoelectronics to produce electrical power or electrical responses. The search for a low-cost thermoelectric material that could achieve high efficiencies and can also be straightforwardly scalable has turned significant attention to the halide perovskite family. Here, we report the thermal voltage response of bismuth-based perovskite derivates and suggest a path to increase the electrical conductivity by applying chalcogenide doping. The films were produced by drop-casting or spin coating, and sulfur was introduced in the precursor solution using bismuth triethylxanthate. The physical-chemical analysis confirms the substitution. The sulfur introduction caused resistivity reduction by 2 orders of magnitude, and the thermal voltage exceeded 40 mV K-1 near 300 K in doped and undoped bismuth-based perovskite derivates. X-ray diffraction, Raman spectroscopy, and grazing-incidence wide-angle X-ray scattering were employed to confirm the structure. X-ray photoelectron spectroscopy, elemental analysis, scanning electron microscopy, and energy-dispersive X-ray spectroscopy were employed to study the composition and morphology of the produced thin films. UV-visible absorbance, photoluminescence, inverse photoemission, and ultraviolet photoelectron spectroscopies have been used to investigate the energy band gap.

Herein, a binary cathode interface layer (CIL) strategy based on the industrial solvent fractionated LignoBoost kraft lignin (KL) is adopted for fabrication of organic solar cells (OSCs). The uniformly distributed phenol moieties in KL enable it to easily form hydrogen bonds with commonly used CIL materials, i.e., bathocuproine (BCP) and PFN-Br, resulting in binary CILs with tunable work function (WF). This work shows that the binary CILs work well in OSCs with large KL ratio compatibility, exhibiting equivalent or even higher efficiency to the traditional CILs in state of art OSCs. In addition, the combination of KL and BCP significantly enhanced OSC stability, owing to KL blocking the reaction between BCP and nonfullerene acceptors (NFAs). This work provides a simple and effective way to achieve high-efficient OSCs with better stability and sustainability by using wood-based materials. This work introduces industrial solvent fractionated LignoBoost kraft lignin (KL) in highly efficient organic solar cells (OSCs) by binary cathode interface layer (CIL) strategy, which can significantly improve the stability of both binary and ternary photoactive layer (PAL) OSC, owing to the passivation of diffusion and reaction between bathocuproine (BCP) and nonfullerene acceptors (NFAs). The results combine sustainable wood-based material with classic interface materials in advance NFA-OSCs.image

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-a-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 (similar to 70 degrees C) and the doping reaction completes in few seconds affording large electrical conductivities (similar to 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.

Owing to its close resemblance to biological systems and materials, soft matter has been successfully implemented in numerous bioelectronic and biosensing applications, as well as in bioinspired computing and neuromorphic electronics. Particularly, organic mixed ionic-electronic conductors possess favourable characteristics for their efficient use in organic electrochemical transistors, electrochemical memory and artificial synapses and neurons. Owing to their mixed ionic-electronic conduction, leading to high amplification, these materials are ideal for translating chemical signals, such as ions or neurotransmitters, into electrical signals, as well as for accurately controlling stable conductance states to efficiently emulate synaptic weights in artificial neural networks. Because these mixed conductors operate with ionic charges - similar to signalling in biological neuronal networks - they also exhibit ideal properties to emulate biological spiking neurons. In this Perspective, we consider the potential of soft matter, especially based on organic mixed conductors, for bioinspired systems and their possible applications. We discuss the potential that these materials have in applications in which low power, conformability and tunability are key, such as smart and adaptive biosensors, low-power in-sensor and edge computing, intelligent agents and robotics, and event-driven systems and biohybrid spiking circuits at the interface with biology. We present a comprehensive perspective of the potential of biomimetic and bioinspired electronics based on soft matter to integrate artificial intelligence into everyday life. Current technologies of bioinspired and neuromorphic electronics still lack a universal framework for integration into everyday life. This Perspective highlights how bioinspired electronics with soft electrochemical matter based on organic mixed conductors can potentially enable the integration of diverse forms of intelligence everywhere.

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 epsilon break = 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 mu W 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. Silk is coated with the n-type polymer poly(benzodifurandione) (PBFDO) resulting in conducting yarn with an extrapolated half-life of 3.2 +/- 0.7 years at ambient conditions, which enables the fabrication of air stable thermoelectric textile generators by embroidery. image

High-performance n-type organic mixed ionic-electronic conductors (OMIECs) are essential for advancing complementary circuits based on organic electrochemical transistors (OECTs). Despite significant progress, current n-type OMIECs often exhibit lower transconductance and slower response times compared to their p-type counterparts, limiting the development of OECT-based complementary circuits. Optimizing the conjugated backbone and side chain structures of OMIECs is critical for enhancing both ion and electron transport efficiencies while maintaining a delicate balance between the two. In this study, hydrophilic polyethylene glycol (PEG) side chains were incorporated into the highly conductive n-type polymer poly(3,7-dihydrobenzo[1,2-b:4,5-b ']difuran-2,6-dione) (PBFDO) backbone to achieve this goal. The incorporation of PEG chains improved ion accessibility, and by adjusting the PEG content, the electronic and ionic transport properties were fine-tuned, ultimately enhancing the performance of OECTs and related p-n complementary circuits. The n-type OECTs based on PBFDO-PEG50wt% demonstrated exceptional transfer characteristics, including a transient response time (tau(ON)) as low as 72 mu s, a high geometry-normalized transconductance exceeding 400 S cm(-1), and an impressive mu C* value surpassing 720 F cm(-1) V-1 s(-1). Notably, the use of PBFDO-PEG50wt% in a complementary inverter resulted in a voltage gain of 20 V/V, more than five times higher than that achieved with unmodified PBFDO (<4 V/V). These findings highlight the importance of balancing electron and ion transport characteristics in OMIECs to achieve high performance in OECTs and their associated circuits, and they validate PEG decoration as an effective approach.