Conductive polymers largely derive their electronic functionality from chemical doping, processes by which redox and charge‐transfer reactions form mobile carriers. While decades of research have demonstrated fundamentally new technologies that merge the unique functionality of these materials with the chemical versatility of macromolecules, doping and the resultant material properties are not ideal for many applications. Here, it is demonstrated that open‐shell conjugated polymers comprised of alternating cyclopentadithiophene and thiadiazoloquinoxaline units can achieve high electrical conductivities in their native “undoped” form. Spectroscopic, electrochemical, electron paramagnetic resonance, and magnetic susceptibility measurements demonstrate that this donor–acceptor architecture promotes very narrow bandgaps, strong electronic correlations, high‐spin ground states, and long‐range π‐delocalization. A comparative study of structural variants and processing methodologies demonstrates that the conductivity can be tuned up to 8.18 S cm−1. This exceeds other neutral narrow bandgap conjugated polymers, many doped polymers, radical conductors, and is comparable to commercial grades of poly(styrene‐sulfonate)‐doped poly(3,4‐ethylenedioxythiophene). X‐ray and morphological studies trace the high conductivity to rigid backbone conformations emanating from strong π‐interactions and long‐range ordered structures formed through self‐organization that lead to a network of delocalized open‐shell sites in electronic communication. The results offer a new platform for the transport of charge in molecular systems.

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Achieving self-assembly of conjugated polymers is necessary to harness their charge transport properties in various applications, including field-effect transistors, sensors, and conductive gels for biomedical applications. Although many processes have been investigated, there are still opportunities for developing new strategies that can lead to materials with improved performances. Particularly, large-scale fabrication of three-dimensional conductive networks formed by the self-assembly of conjugated polymers and low-molecular-weight gelators (LMWGs), but with conjugated polymers at much lower quantity, would be advantageous. LMWGs can be selected from an extensive library of available systems and can be directed to self-assemble in various conditions. However, the simultaneous self-assembly of LWMGs and conjugated polymers is not fully understood. Here, we report a simple pathway for the self-assembly of poly­(3-hexylthiophene) (P3HT), a conjugated polymer, in chloroform in the presence of di-Fmoc-l-lysine, an LMWG. Di-Fmoc-l-lysine was selected as the LMWG because it does not have significant interactions with P3HT. P3HT and di-Fmoc-l-lysine in chloroform form gels with decreasing temperature. UV–vis spectroscopy provides an insight into the photophysical response of the gelation process, revealing the self-assembly of P3HT in the gel network. The scattering experiments further capture the self-assembly of the P3HT network. The nanofibrillar microstructure has been captured using atomic force microscopy (AFM) for the gels without and with P3HT, where both P3HT and di-Fmoc-l-lysine form nanofibers independently. Both these nanofibers coexist and intermingle, displaying conductive domains in the dried films captured by conductive AFM. The conductive nanofibers form a percolated network in the dried samples, leading to bulk electrical conductivity similar to that of pristine P3HT films. This is achieved with only 20% P3HT content and the balance insulating di-Fmoc-l-lysine molecules. Our results provide a fundamental understanding of the self-assembly of P3HT in the presence of an LMWG, resulting in a conductive nanofibrillar network. Such knowledge can readily be implemented in other conjugated polymeric systems. The approach presented here has potential applications towards fabricating conductive gels for biomedical and sensor applications and large-scale processing of thin films for optoelectronic applications.

Phosphate oxyanions play central roles in biological, agricultural, industrial, and ecological processes. Their high hydration energies and dynamic properties present a number of critical challenges limiting the development of sensing technologies that are cost‐effective, selective, sensitive, field‐deployable, and which operate in real‐time within complex aqueous environments. Here, a strategy that enables the fabrication of an electrolyte‐gated organic field‐effect transistor (EGOFET) is demonstrated, which overcomes these challenges and enables sensitive phosphate quantification in challenging aqueous environments such as seawater. The device channel comprises a composite layer incorporating a diketopyrrolopyrrole‐based semiconducting polymer and a π‐conjugated penta‐t‐butylpentacyanopentabenzo[25]annulene “cyanostar” receptor capable of oxyanion recognition and embodies a new concept, where the receptor synergistically enhances the stability and transport characteristics via doping. Upon exposure of the device to phosphate, a current reduction is observed, consistent with dedoping upon analyte binding. Sensing studies demonstrate ultrasensitive and selective phosphate detection within remarkably low limits of detection of 178 × 10−12 m (17.3 parts per trillion) in buffered samples and stable operation in seawater. This receptor‐based doping strategy, in conjunction with the versatility of EGOFETs for miniaturization and monolithic integration, enables manifold opportunities in diagnostics, healthcare, and environmental monitoring.

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