Interest in high-spin organic materials is driven by opportunities to enable far-reaching fundamental science and develop technologies that integrate light element spin, magnetic, and quantum functionalities. Although extensively studied, the intrinsic instability of these materials complicates synthesis and precludes an understanding of how fundamental properties associated with the nature of the chemical bond and electron pairing in organic materials systems manifest in practical applications. Here, we demonstrate a conjugated polymer semiconductor, based on alternating cyclopentadithiophene and thiadiazoloquinoxaline units, that is a ground-state triplet in its neutral form. Electron paramagnetic resonance and magnetic susceptibility measurements are consistent with a high-to-low spin energy gap of 9.30 × 10⁻³ kcal mol⁻¹. The strongly correlated electronic structure, very narrow bandgap, intramolecular ferromagnetic coupling, high electrical conductivity, solution processability, and robust stability open access to a broad variety of technologically relevant applications once thought of as beyond the current scope of organic semiconductors.

Conductive hydrogels are promising materials with mixed ionic‐electronic conduction to interface living tissue (ionic signal transmission) with medical devices (electronic signal transmission). The hydrogel form factor also uniquely bridges the wet/soft biological environment with the dry/hard environment of electronics. The synthesis of hydrogels for bioelectronics requires scalable, biocompatible fillers with high electronic conductivity and compatibility with common aqueous hydrogel formulations/resins. Despite significant advances in the processing of carbon nanomaterials, fillers that satisfy all these requirements are lacking. Herein, intrinsically dispersible acid‐crystalized PEDOT:PSS nanoparticles (ncrys‐PEDOT_X) are reported which are processed through a facile and scalable nonsolvent induced phase separation method from commercial PEDOT:PSS without complex instrumentation. The particles feature conductivities of up to 410 S cm⁻¹, and when compared to other common conductive fillers, display remarkable dispersibility, enabling homogeneous incorporation at relatively high loadings within diverse aqueous biomaterial solutions without additives or surfactants. The aqueous dispersibility of the ncrys‐PEDOT_X particles also allows simple incorporation into resins designed for microstereolithography without sonication or surfactant optimization; complex biomedical structures with fine features (< 150 µm) are printed with up to 10% particle loading . The ncrys‐PEDOT_X particles overcome the challenges of traditional conductive fillers, providing a scalable, biocompatible, plug‐and‐play platform for soft organic bioelectronic materials.

The emerging field of bioelectronics leverages the optoelectronic properties of synthetic materials to interface with living systems. The convergence of modern electronics with biology has offered lifesaving medical treatments, with applications related to drug delivery, regenerative engineering, and continuous biosignal monitoring for healthcare on the horizon. This next generation of bioelectronic technologies requires an intimate biointerface, necessitating electroactive materials which are both mechanically and physiochemically compatible. Organic systems such as conjugated polymers offer an alternative design space for electroactive materials that are mechanically compatible (flexible, stretchable, conformal) and chemically tunable through various well-established synthetic methods and can therefore be tailored for integration with biological systems. Currently, conjugated polymers utilized for bioelectronic applications consist of prominent high-performing materials emerging from adjacent organic electronic communities with slight chemical modifications, and are therefore generally not well-suited for the entire lifecycle of a biomaterial. While early investigations have demonstrated the potential of such conjugated polymers as semiconductors and conductors in vivo, their limited biodegradability and long-term biocompatibility have slowed widespread adoption and clinical translation. To aid in the development of the next generation of bioelectronic materials, this review details various synthetic strategies to endow a conjugated material with degradability and biocompatibility. Prominent examples of conjugated materials are used to illustrate design principles, current limitations, and future directions towards such electroactive materials. The main factors that need to be considered for the rational design of biodegradable and biocompatible conjugated polymers for bioelectronic applications are highlighted, with future directions emphasized.

Donor–acceptor (DA) conjugated polymers provide an important platform for the development of solution-processed optoelectronic devices. The complex interrelation between electronic properties and conformational disorder in these materials complicates the identification of design guidelines to control the bandgap at low energies, limiting the design of new optoelectronic and device functionalities. Here, we demonstrate that DA polymers comprised of exocyclic olefin substituted cyclopentadithiophene donors, in combination with conventional electron acceptors, display very narrow optical bandgaps (1.2 > E^opt _g > 0.7 eV) and primary photoexcitations extending into the shortwave infrared. Theoretical calculations reveal fundamental structure–property relationships toward bandgap and energy level control in these spectral regions. Bulk heterojunction photodiodes fabricated using these new materials demonstrate a detectivity (D*) of > 10¹¹ Jones within a spectral range of 0.6–1.43 μm and measurable D* to 1.8 μm, the longest reported to date for conjugated polymer based systems.