Ronny Timmreck, Selina Olthof, Karl Leo, and Moritz K. Riede A key feature of stacked organic solar cells is an efficient recombination contact at the interface between the solar cells in the stack. Here, an electron current has to be converted into a hole current without loss of energy. Furthermore, the recombination contact has to be highly transparent. We ... [J. Appl. Phys. 108, 033108 (2010)] published Thu Aug 5, 2010.