A solution-processed n-type conducting polymer with ultrahigh conductivity

Conducting polymers (CPs) with high conductivity and solution-processability have gained great advances since the pioneering work on doped polyacetylene1-3, thus creating the new field of 'organic synthetic metals'4. Various high-performance CPs have been realised, which enable the applications of multiple organic electronic devices5,6. Nevertheless, most CPs exhibit hole-dominant (p-type) transport behaviour7,8, while the development of n-type analogues lags far behind and few exhibits metallic state, typically limited by low doping efficiency and ambient instability. Here, we present a facilely synthesized highly conductive n-type polymer poly(benzodifurandione) (PBFDO). The reaction combines oxidative polymerisation and in situ reductive n-doping, dramatically increasing the doping efficiency, and doping level of almost 0.9 charge per repeating unit can be achieved. The resultant polymer exhibits a breakthrough conductivity over 2000 S cm-1 with excellent stability and an unexpected solution-processability without extra side chains or surfactants. Additionally, detailed investigations on PBFDO reveal coherent charge transport properties and existence of metallic state. The benchmark performances in electrochemical transistors and thermoelectric generators are further demonstrated, thus paving the way for application of the n-type CPs in organic electronics.