Ambipolar polymer finite-space probing of voltage-driven counterion-insertion-coupled charge transport for wide-voltage energy storage

• Potentiostatic deposition controls donor-acceptor interplay in poly[NDI-(DTP) 2 ] • Finite-space approach probes ambipolar counterion-coupled charge transport • Wide-voltage operation facilitated well-separated donor-acceptor redox conduction • 2V poly[NDI-(DTP) 2 ] supercapacitor delivered 12.2 µWh cm −2 at 389 µW cm −2 Wide-voltage faradaic storage in ambipolar polymer electrode materials derives from p- and n- type doping and dedoping triggered by their electrooxidation and electroreduction. However, the role of ambipolar polymer layer-confined molecular packing of donor and acceptor units in controlling dynamics of reversible electrochemical doping and, thereby, energy storage performance remains poorly understood. Another problem arises from mutual donor-acceptor interactions within the ambipolar layer architecture, where specific spatial arrangements can perturb electronic coupling and ion-access pathways, thereby altering charge transport. In that regard, we dissected the fabrication conditions of the ambipolar poly[NDI-(DTP) 2 ] electrode material to achieve a balanced interaction between its alternatingly conjugated dithienopyrrole donor and naphthalene diimide acceptor units. Electrochemical measurements and atomic force microscopy imaging revealed that potentiostatic electrodeposition imposes a privileged molecular arrangement in the studied ambipolar polymer. Finite-space probing of the potentiostatically arranged poly[NDI-(DTP) 2 ] layer resolved the ambipolar charge transport dynamics and showed well-balanced donor and acceptor charge storage contributions despite differing p- and n- doping and dedoping rates. This understanding guided the assembly of a poly[NDI-(DTP) 2 ]-based supercapacitor operating at 2.0 V, delivering an energy density of 12.2 µWh cm −2 at a power density of 389 µW cm −2 . Our insights provided a general framework for probing reversible solid-solution counterion insertion to redox-active ambipolar polymer electrodes for high-voltage energy storage applications.