Multiple electrochemical doping-induced insulator-to-conductor transitions observed in the conjugated ladder polymer polybenzimidazobenzophenanthroline (BBL)

Spectroelectrochemical techniques have been used to study doping-induced reactions in conjugated polymers. Here, we report results on reduction reactions (n-doping) of the conjugated ladder polymer polybenzimidazobenzophenanthroline (BBL). The spectra are recorded in situ during applied potential in a three-electrode spectroelectrochemical cell. The spectral and thus the structural changes during the reduction (n-doping) of the polymer film at different electrode potentials are discussed. In contrast to most of the other conjugated polymers, this polymer shows four reversible redox reactions during n-doping, corresponding to various insulating and conducting forms of BBL.