Inverted Organic Solar Cells

Intense research has been carried out to obtain high-efficiency, stable, low-cost, and high-speed production of organic solar cells. Organic photovoltaics (OPVs) devices are based on carbon-based organic semiconductors in which charge transport is mainly by the delocalization of electrons along conjugated polymer backbones. At early stages, most organic solar cells, including single layer, bilayer, and bulk heterojunction devices, were fabricated using normal device structure by sandwiching photoactive layers between two electrodes. Generally, higher work function electrode indium tin oxide (ITO) served as the anode and the low work function electrode Al as cathode. However, efficiency of organic solar cells with both a single layer and bilayers was limited by exciton diffusion length and the area of donor– acceptor interface. Device fabrication using solution processing techniques of all involved layers is the ultimate goal of organic solar cells so that roll-to-roll processing and mass production are viable, which can reduce the cost to a great extent.