Thin films of interacting dimers of 4,4'-bis(1,2,3,5-dithiadiazolyl), sandwiched by ITO and Al, exhibit an anomalous transient current, due to a significant imbalance between the hole and electron mobilities and bulk polarization. We propose a new operational principle for organic optoelectronic conversion systems, which efficiently generates alternating photocurrent without being affected by the disadvantages of organic materials, such as poor mobility. (C) 2009 Elsevier B.V. All rights reserved.