Nolasco, J.C.J.C.NolascoRamos-Ortiz, G.G.Ramos-OrtizMaldonado, J.L.J.L.MaldonadoBarbosa-Garcia, O.O.Barbosa-GarciaEcker, B.B.EckerHauff, E. vonE. vonHauff2022-03-052022-03-052014https://publica.fraunhofer.de/handle/publica/24145410.1063/1.4863755By exploring the origin of the saturation current (J0), we show that the polymer/cathode interface determines the open circuit voltage (Voc) in polymer:fullerene bulk heterojunction solar cells. We fabricate and characterize P3HT:PCBM solar cells and compare their electrical characteristics using as reference P3HT/cathode Schottky diodes. We demonstrate with thermionic emission theory that J0 has the same origin in both devices. Thus, a general barrier-dependent expression for Voc, valid for non-ohmic cathode contacts is proposed and discussed.en621journal article