Role of dielectric properties in organic photovoltaic devices

We have fabricated organic photovoltaic devices via layer-by-layer electrostatic self-assembly technique with varied number of donor/acceptor interfaces. Upon illumination, the short-circuit current of the devices depended on the number of such interfaces. We have studied impedance spectroscopy of the photovoltaic cells under dark and illumination conditions. We compared the changes in bulk resistance of the device and relative dielectric constant of the active material with short-circuit current of the devices due to illumination. The results show that the photovoltaic devices should be designed in such a way that the dielectric constant of the active material exhibits large decrease under illumination.