Generation profile shape dependent performance of mobility imbalanced organic solar cells

Generation profile shape dependence of the device performance in organic solar cells have been investigated. The device performance is analyzed using extracted device parameters by fitting the device characteristics to the equivalent circuit based on single diode model. It is found that for organic solar cells with an imbalance in hole and electron mobility, the device performance greatly depends on the generation profile shape. With the lowest saturation current density and ideality factor combined with highest shunt resistance and photo-current density, the generation profile with peak generation density near the hole collecting contact has the best device parameters and therefore optimal in terms of extraction. In terms of actual devices the peak generation density occur near the front contact. Therefore for mobility imbalanced devices, standard device architecture where the front contact is designated as the hole collecting contact has much better performance compared to the inverted device architecture where front contact is designated as the electron collecting contact. For the mobility balanced devices the generation profile shape dependence of the device performance is greatly reduced, but when the barrier heights of the end contacts are different, some dependence in device performance on generation profile shape can be detected. In this case the best performance is achieved when peak generation occur further away from lower barrier height electrode.