Abstarct: Nowadays, more than seventy percent of the energy consumed on world comes from fossil fuels. These fuels not only produce high levels of pollution, but will expire in next 50 years. Therefore we need to develop renewable energy sources such as solar energy. Solar energy is one of best candidates for stable and clean source of energy. Solar cells are devices consist of semiconductors which convert solar radiation energy to electrical energy directly. Today inorganic solar cells are produced industrially with high efficiency, but their production cost is very high. Therefore, new types of materials such as Organic semiconductors have attracted much attention during the last two decades. Organic solar cells have several advantages, such as low production cost, flexibility, low weight and ability to fabricate in large area. Therefore In this research, we have studied the physics and properties of organic semiconductors for using in solar cells. In this work, Some specimens of bilxayer organic solar cells consists of phthalocyanine (CuPc), as a hole acceptor, and fullerene (C60), as an electron acceptor, with heterostructures of ITO/CuPc(20nm)/C60(40nm)/Al(80nm) and ITO/CuPc(20nm)/C60(40nm)/BCP(8nm)/Al(80nm) have been produced by thermal evaporation technique in high vacuum. Current-voltage curves of cells have been measured by solar simulator under AM1.5 standard illumination. By using exciton blocking laxyer (EBL) at the organic/cathode interface, short circuit current density was increased and consequently the performance of device was improved. Finally, absorption spectra of thin films used in cells and also itself cell were measured and analyzed. We observed that in CuPc/C60 bilxayer system, CuPc and C60 have complementary absorption spectra in the whole visible spectral range. Also we found that with increasing laxyer thickness and material purity the absorption value is increased. By using X ray diffraction (XRD) the structures of laxyers were investigated.