Exploring the exciton dissociation process at a donor-acceptor heterojunction in both time and space via an induced Stark shift

The dissociation of excitons at a donor-acceptor interface in organic photovoltaic devices is an important but poorly understood process that takes place over multiple length and time scales. Here, we introduce a method to resolve photoinduced charge movement at an organic heterojunction in both time and space through observation of the Stark shift induced in a nearby J-aggregate probe layer. Using ultrafast transient absorption measurements, we show that this technique provides an opportunity to quantify the recombination and separation dynamics of geminate charge pairs over the entire sub-picosecond to millisecond range of relevant time scales.