Charge carrier mobility dependent open-circuit voltage in organic and hybrid solar cells

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 (µ_g and µ_n) 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 (µ_g) and hole (µ_n) mobilities in the blend. It is found that the V_∝ increases with the increase of the mobility ratio µ_e / µ_h . The most loss in V_∝ is contributed by the energetics of the donor and acceptor materials.