In order for organic bulk heterojunction solar cells to compete with the traditional inorganic cells, higher power conversion efficiencies are desirable. A characteristic of organic solar cells is their narrow absorption window, compared to the absorption band of inorganic semiconductors. A possible way to capture a wider band of the solar spectrum - and thus increasing the power conversion efficiency - is using two or more solar cells with different bandgaps in a row, referred to as a multi-junction solar cell. In this article, we study the theoretical efficiency potential of three organic cells in a row, i.e. a triple-junction. We study the influence of the energy levels of donor and acceptor, as well as different absorption windows of the subcells. We not only study the light harvesting potential of the usual monolithic configuration, but also consider a stacked set-up. Ideal material characteristics are obtained from these calculations, giving an idea of how the ideal organic triple-junction cell should look like. An interesting result is that it is not necessary to develop photovoltaic organic materials with an absorption window broader than 300 nm for triple-junctions, because hardly any efficiency gain can be achieved by a broader absorption window.