Energy Losses in Small-Molecule Organic Photovoltaics

After intense research and development organic solar cells have matured among the family of thin-film photovoltaic technologies. On the laboratory scale they reach power conversion efficiencies in excess of 10%. Together with other attractive features, like transparency or the compatibility with low-cost, large area processing, they open reasonable perspectives for their commercialization. However, in order to close the gap to established inorganic technologies, primarily crystalline silicon, the fundamental understanding of loss processes has to be improved. First and foremost, this concerns the energy loss between the optical gap for light absorption and the open-circuit voltage of the cell. Here, the scientific background for the different mechanisms of energy losses in organic photovoltaic cells together with current approaches toward their reduction is presented.