Controlling ion-polymer interactions in organic mixed ionic-electronic conductors is crucial for optimizing device performance in applications ranging from bioelectronics and energy storage to photonics. Achieving this requires a molecular-level understanding of how ion uptake, solvation and polymer structure evolve during electrochemical doping. Here using a multimodal operando approach, we uncover an unexpected response in the prototypical n-type ladder polymer poly(benzimidazobenzophenanthroline) (BBL) on doping with protic cations such as ammonium. At high doping levels, strong ion-polymer interactions (primarily hydrogen bonding) between cations and the BBL backbone promote charge localization and disrupt ion hydration, leading to a pronounced reduction in mass and thickness. Operando 2H NMR identifies water expulsion, rather than ion removal, as the origin of this deswelling. Our combined experimental and modelling results reveal a previously unobserved regime of ion-polymer coupling in organic mixed ionic-electronic conductors, establishing a framework for material design and applications that span (bio-)electronics to photonics.

The synthesis of n-type semiconductors traditionally relies on the environmentally harmful Stille organotin polymerization. Here, we report the optimized direct arylation polymerization (DARP) of an electron-transporting polymer, poly[2,7-bis(2-decyltetradecyl)-4-methyl-9-(2 '-methyl-[5,5 '-bithiazol]-2-yl)benzo[lmn]-[3,8]phenanthroline-1,3,6,8(2H,7H)-tetraone], P(NDI2DT-Tz2). A series of PNDITZ-Mn polymers with molecular masses (M n) from 6.5 to 32.9 kg mol-1 was synthesized and investigated for charge transport and thermoelectric properties. Optimized DARP conditions yielded PNDITZ-19 K (M n/D = 18.8 kg mol-1/2.8), comparable to Zn-PNDITZ prepared via the anionic zinc protocol (16.4 kg mol-1/2.39). Thermal, UV/vis, and VT-NMR analyses confirmed that PNDITZ-19 K displays photophysical properties and structural integrity indistinguishable from those of Zn-PNDITZ. Charge transport and thermoelectric measurements gave sigma approximate to 2 & times; 10-2 S cm-1 and a power factor near 1 mu W m-1 K-2. GIWAXS analysis revealed that polymer crystallinity correlates directly with M n/D, with PNDITZ-19 K showing the best performance across the series and approaching that of Zn-derived materials. Notably, DARP-synthesized P(NDI2DT-Tz2) achieved a 15-fold reduction in the E-factor (7.23 vs 108.65), highlighting its much lower environmental footprint. These results establish DARP as a sustainable and efficient method for producing high-quality n-type semiconducting polymers.

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.

Chemical doping is crucial for fine-tuning the electronic properties of organic semiconductors (OSCs) and enhancing device performance across various technologies. While several methods for controlled dopant distribution have been explored, achieving lateral doping gradients via simple solution processing remains challenging. Here we present a gold-activated persulfate doping strategy in which persulfate is catalytically activated at gold surfaces to generate SO4 center dot- radicals that locally oxidize (p-dope) the OSCs. This reaction creates a lateral doping gradient extending outwards from the gold interface, as verified by spectroscopic and electrical characterization. The approach is broadly applicable to OSCs spanning a 1.5-eV ionization potential range and yields conductivities >1,900 S cm(-1). To demonstrate the impact of this method, we applied gold-activated persulfate doping to modulate contact regions in solution-processed organic field-effect transistors, achieving reduced contact resistance and improved charge-carrier mobility. This simple, scalable approach enables the formation of lateral doping gradients from solution and offers new opportunities for interfacial tuning in organic electronics.

This roadmap presents key advances and future directions in the field of the conducting polymer polyethylene dioxythiophene (PEDOT), with a focus on its role as multifunctional material in emerging electronic applications. It covers a broad spectrum of topics, including self-healing materials, plant bioelectronics, energy harvesting and storage, and neural interfaces. The roadmap also addresses recent progress in the synthesis and functionalization of PEDOT derivatives, as well as insights from molecular dynamics simulations and transport physics. Emphasis is placed on a range of processing techniques, such as electropolymerization, vapor phase polymerization, and 3D printing, and their implications for device performance. Specific applications explored include thermoelectrics, biosensors, organic electrochemical transistors, and advanced bioelectronic platforms for neuromodulation, stretchable electronics, and neuromorphic computing. This collective effort aims to serve as a comprehensive resource outlining the current state of PEDOT research and identifying challenges and opportunities for its integration across diverse electronic technologies.

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.