We show that by introducing a polymerized fluorocarbon film (CFx) on indium tin oxide (ITO), stability of CuPc/C60 organic photovoltaic device can be improved. While the efficiency of a standard device decreases from 1.5% to 0.7% after 2000 h of storage and intermittent operation, a CFx-buffered device shows negligible changes (1.6% throughout 2000 h). We found that C60 is influenced by the ITO substrate. X-ray photoemission studies show that reactive −O• species on the ITO surface were minimized after CFx polymerization. Reduction of such species from organic layers is considered a major cause for the stability enhancement in the CFx-buffered device.