A trilayer ultrathin-film model concept had been adapted to maximize optical absorption of organic photovoltaic cells (OPVs) with a structure of transparent-electrode/highly-absorbing active material/metal. As demonstrated, device with the structure of ITO/Lead phthalocyanine (SubPc):Buckerminster fullerene (C60) (1:4wt%)/Al had been studied. It is found that more than 90% optical absorption can be obtained in the device with a broaden wavelength range of 480–620nm. The calculated optical electric fields shows that the unusually high optical absorption is due to the enhanced optical interference inside the OPVs device. This work paved a new way to design the OPVs device.