Non-zero output from a symmetrical organic photovoltaic device

A symmetrical bulk heterojunction organic photovoltaic device is fabricated to study the transport properties of charge carriers in the organic active layer. It is found that such a symmetrical structure exhibits an asymmetrical current-voltage behavior, with a finite open-circuit voltage of about 50 mV caused by illumination. The polarity can be switched by changing the illuminated electrode from one to the other, accompanied by the swap of the cathode and anode. The operation mechanism of the symmetrical device and the charge carrier transport are explained by a detailed model involving two opposite types of the transport paths.