A better understanding of the open-circuit voltage (V∝) related losses in organic solar cells (OSCs) is desirable in order to assess their photovoltaic performance. We have derived V∝ as a function of charge carrier mobilities (µg and µn) for organic and hybrid solar cells by optimizing the drift-diffusion current density. The V∝ thus obtained depends on the energy difference between the highest occupied molecular orbital (HOMO) level and the quasi-Fermi level of holes of the donor material and on the ratio of the electron (µg) and hole (µn) mobilities in the blend. It is found that the V∝ increases with the increase of the mobility ratio µe / µh . The most loss in V∝ is contributed by the energetics of the donor and acceptor materials.