Abstract: In this work, copper phthalocyanine （CuPc） and buckminsterfullerene （C₆₀） were used as donor and acceptor, resprcively, in organic photovoltaic（PV） solar cells with a structure of ITO/CuPc/C₆₀/Al. It was found that the performance of PV was sensitive to the thickness of active layer（CuPc and C₆₀）. Because of the limited exciton diffusion length L, i.e. the characteristic distance over which excitons migrate before recombining, the thickness of a photoactive layer in organic solar cells is often limited to the values typically of the order of L. In present work, the optimal thicknesses ratio of CuPc to C₆₀ as active layers were discussed in deail.