Abstract
Organic solar cells exhibit both electrode/photovoltaic (E/P) interface and
donor/acceptor (D/A) interface in controlling the critical photovoltaic processes. Here, on the
basis of the efficient PTB7:PC71BM solar cells, our studies on magneto-photocurrent with
external bias provide the first evidence that the E/P interface and D/A interface are dynamically
coupled at device-operating condition. Specifically, we observe a significant decrease (90%) in the
critical bias required to completely dissociate the charge transfer (CT) states at D/A interface by
changing the E/P interface with increased interface dipole field from ZnO to the polyelectrolyte
(PFN). The experimental results demonstrate that strong dipole field at the E/P interface can
effectively decrease the electron−hole binding energy at D/A interface through the enhancement
of built-in field applied on CT states. Clearly, our experimental studies provide new insight on the
interfacial engineering through addressing the dynamic coupling between E/P interface and D/A interface in organic bulkheterojunction
solar cells toward further improvement on photovoltaic efficiencies.