A water-processable n-type polymeric ink with conductivities exceeding 1,000 S cm−1

<h2>Summary</h2> High-performance n-type conducting polymers remain scarce, with most requiring toxic and/or hazardous solvents for processing. Here, we report a water-processable poly(benzodifurandione) (PBFDO) ink that achieves conductivities up to 1,400 S cm⁻¹, the highest reported for n-type conjugated polymers from green solvents. The use of long-tailed amphiphilic zwitterions to stabilize the PBFDO nanoparticles creates a hydrophobic interfacial barrier that also suppresses oxidative side reactions (de-doping) with oxygen and water, resulting in aqueous dispersions that are stable for over 160 days. This molecular-level control preserves structural order in cast films, enabling sustainable and scalable fabrication of thin films with a remarkable power factor of 184 μW m⁻¹ K⁻²—among the largest for water-processed n-type polymers—highlighting their potential for high-performance thermoelectrics. By combining exceptional electronic performance, long-term stability, and sustainable processing, this work paves the way for environment-friendly, scalable manufacturing of next-generation organic electronic and energy-harvesting devices.