Recent progress in organic photovoltaics: device architecture and optical design

Research on organic photovoltaic (OPV) materials and devices has flourished in recent years due to their potential for offering low-cost solar energy conversion. With a deepened understanding on the fundamental photovoltaic processes in organic electronic materials and the development of tailored materials and device architectures, we have seen a rapid increase in the efficiency of OPV devices to over 10%, which attracts tremendous commercial interests for further development and manufacturing. Here, we review recent progress in the field of organic photovoltaics, particularly on various innovative device architectures and optical designs to maximize the power conversion efficiency of OPV cells for a given set of photoactive donor and acceptor materials. Following an introduction of the basic device operation of organic photovoltaic cells and the advances in active materials, we firstly present different device architectures that have been used to optimize the charge generation and collection characteristics within the OPV devices. We then discuss various methods to manage and manipulate the light wave propagation in OPV devices for more complete absorption of the incident light, an important area that has been underexplored so far.