Diketopyrrolopyrrole-Based Mixed Ionic–Electronic Conductors: From Molecular Design to Multifunctional Electrochemical Devices

Organic mixed ionic–electronic conductors (OMIECs) have emerged as a versatile class of functional materials, enabling a wide range of advanced electrochemical technologies including bioelectronics, electrochromic systems, energy storage devices, and neuromorphic platforms. Among OMIEC scaffolds, diketopyrrolopyrrole (DPP)-based donor–acceptor conjugated polymers have gained prominence due to their modular structure, redox stability, and tunable charge transport characteristics. In this Spotlight on Applications, we highlight recent efforts to develop DPP-based polymers for high-performance electrochemical devices. We examine how backbone engineering, side-chain design, and polymer–ion interactions collectively influence mixed conduction, redox kinetics, volumetric capacitance, and operational stability. Modifications to donor (acceptor) units and π-bridges enable tuning of ionization potentials, polaron delocalization, and ambient durability. Concurrently, oligoethylene glycol (OEG) side chains enhance ion uptake and promote dynamic ion–polymer interactions critical to device performance. These design strategies have enabled multifunctional DPP-based devices across several platforms. As cathodes in solid-state lithium batteries, they deliver high redox potentials (∼2.2 V vs Li⁺/Li), ultrafast rate capabilities (up to 500 C), and long cycle life, enabled by conjugated backbones and stable carbonyl redox centers. In organic electrochemical transistors (OECTs), DPP-based polymers exhibit ambipolar transport and operate at low threshold voltages, making them well-suited for bioelectronic and neuromorphic applications. In electrochromic devices, DPP polymers demonstrate high coloration efficiency, broad spectral tunability, and prolonged open-circuit memory, driven by polaron stability and selective polymer–anion interactions. By integrating molecular design with device-level functionality, DPP-based OMIECs provide an exciting platform for developing the next generation of intelligent, adaptive, and energy-efficient organic electronics.