An efficient organic photovoltaic (OPV) cell with an indium-tin-oxide/CuPc/C60/Ag structure has been investigated by changing the film thickness of organic layers. A high open-circuit voltage (VOC) of 0.5 V,a short-circuit current density (JSC) of 5.81 mA/cm2,and a high power conversion efficiency (ηp) of 1.2% were achieved at an optimum film thickness. The results demonstrate that material thickness is an important factor to cell optimization,especially for maximizing the absorp-tion rate as well as reducing the cell resistance. Experimental results also indicate that the power conversion efficiency increases from 1.2% to 1.54% as a BCP exciton blocking layer of 10 nm is introduced.