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Charge trapping under transient conditions in polybithiophene/polyxylylviologen (PBT/PXV) bilayers has been studied. In situ visible transmission spectroscopy was used to determine the outer layer redox composition during and immediately following outer layer reduction. Little inner layer reduction (“n-doping”) is required to initiate charge trapping via inner layer mediated reduction of outer layer viologen sites. The viologen radical is the sole initial product of outer layer reduction, but PXV 0 production commences before one-electron reduction of the outer layer is complete. Under transient conditions, there is a build-up of fully reduced PXV 0 at the PBT/PXV interface, and the rate limiting step shifts from inner to outer layer charge transport. On longer time scales, PXV 0 and PXV 2+ conproportionation can be observed in partially reduced outer layers as they equilibrate. |
