Inverted organic solar cells based on poly[N-90 0-hepta-decanyl-2,7-carbazole-alt-5,5-(40,70-di-2-thienyl-20,10,30-benzothiadiazole)/[6,6]-phenyl-C61-butyric acid methyl ester [PCDTBT: PC70BM] bulk-heterojunction (BHJ) were elaborated. We have studied the effects of thermal annealing of PCDTBT: PC70BM active layer on electrical properties in dark condition of different elaborated inverted structures. The PCDTBT: PC70BM thin film was sandwiched between indium tin oxide (ITO)/ZnO front and PEDOT:PSS/aluminum (Al) back electrodes in which PEDOT:PSS was a hole transporting layer (HTL) and ZnO was an electron transport layer (ETL). The elaborated inverted device structure was ITO/ZnO/PCDTBT: PC70BM/PEDOT:PSS/Al. The active layer of organic devices were annealed at different temperatures: as cast, 70°C, 110°C, 150°C and 190°C. In this study, we aimed to elaborate inverted organic solar cells (OSCs) with better electrical parameters for photovoltaic applications using different temperatures. The electrical properties have been studied using J–V measurement in dark condition. The different electrical parameters, such as the barrier height ϕb, the ideality factor n and the series resistance Rs, were calculated. The experimental result shows that these parameters depended strongly on the annealing temperature.