A redox active polymer network film containing donor-node-acceptor (D-n-A) units was prepared by using the electropolymerization (EP) of the precursor (4Cz-4Cl-PBI). The polymer film was characterized by the UV-vis absorption, FT-IR, SEM, XRD and electrochemical techniques. The precursor contains phenyl connected two carbazoles (D) linked by the two sp(3) N-nodes on both sides of a tetrachloro-substituted PBI (A). The two N-nodes block the conjugation between D and A units, resulting in an independent redox activity (from D and A) and doping behaviors. This novel concept of the D-n-A polymer effectively increases the conductivity and stability of the n-doped state. The EP film can be prepared on ITO and flexible electrodes with large area, smooth surface morphology, controllable thickness, and nanoporous structure. Notably, the polymer network film showed ambipolar doping characteristics, with high capacitance (both n- and p-doped states). These properties are very suitable to construct ambipolar electrodes for the flexible supercapacitors. The flexible solid-state supercapacitor devices made from poly(4Cz-4Cl-PBI) network film can readily charge and discharge (fast electron transfer). The flexible supercapacitor showed a very large potential window (2.2 V) and high power density (17.4 W cm(-3)).