Direct probing of the selective electron and hole accumulation at organic/organic interfaces in a triple-layer organic device by time-resolved optical second harmonic generation

By directly probing the electric field changes across the fullerene active layer with time-resolved optical second harmonic (SH) generation method, the selective carrier accumulation processes at organic/organic interfaces in an Au/pentacene/fullerene/polyimide/indium tin oxide triple-layer device were revealed. On the basis of the Maxwell-Wagner effect, it was shown that injected holes preferably accumulated at the pentacene/fullerene interface, resulting in a fast increase of the generated SH intensity around 10 −5 s; while the injected electrons transported until to the fullerene/polyimide interface, resulting in a delayed decrease of the SH intensity after 10 −3 s.