Charge accumulation at the interface of polymer/fullerene studied by double-pulse photocurrent responses

Transport mechanism of photogenerated carriers in composite films based on Poly [2-methoxy,5-(2′-ethylhexyloxy)-1,4,-phenylene-vinylene] (MEH-PPV) doped with fullerene (C60) is investigated by double-light-pulse induced photocurrent responses. Charge accumulation is found in low concentration ranges of C60, while at high C60 concentration (50 wt%), the same feature is completely absent. Charge accumulation at the interface between MEH-PPV and C60 directly reduces the external quantum efficiency of composite devices.