Polymer solutions of p(NDI-T2 P75) were prepared by dissolving the polymer in chloroform at a mass concentration of 11.7 mg/mL. Prior to deposition, the RRDE was cleaned and polished with Al2O3 (particle size 0.05 μm) to a mirror finish. To create thick polymer films (estimated thickness = 1 μm), 10 μL of this solution was dropcast onto the glassy carbon disk of a rotating ring disk electrode (RRDE) (E6R1, Pt ring, polyether ether ketone (PEEK) shrouded, Pine Research) and the electrode was rotated at 400 r.p.m. for 2 min.