Capacitance measurements to directly investigate exciton behaviors in organic photovoltaic materials

The major obstacle to directly determining exciton behaviors in common organic photovoltaic materials (e.g. fullerene) is the absence of room-temperature luminescence. Regarding this issue, the capacitance dependences on incident light intensity and electric field are investigated for several typical organic photovoltaic materials. Distinctive correlations between capacitance and light intensity/electric field are observed for different samples. Moreover, the exciton dissociation probability of fullerene and the charge density of pentacene are extracted from the capacitance–voltage (C–V) characteristics. All these results demonstrate a straight pathway to survey exciton behaviors in those materials with almost no luminescence at room temperature.