We model the absorption enhancement in organic photovoltaic devices induced by incorporating Al, Ag, and Au nanoparticles in the active layer. We find that Al nanoparticles should yield significantly greater enhancement than Ag or Au. This is because the much higher plasma frequency of Al ensures a better overlap between plasmon resonance and absorption band of organic semiconductors. Our predictions are verified experimentally by demonstrating enhanced absorbance in a poly(3-hexylthiophene-2,5-diyl): [6,6]-phenyl C61 butyric acid methyl ester layer with embedded functionalized Al nanoparticles. (C) 2011 American Institute of Physics. [doi:10.1063/1.3574091]