Effect of spherical metallic nanoparticles in active layer on absorption enhancement in organic solar cells

It has been demonstrated experimentally that the presence of metallic nanoparticles (MNPs) in the active layer assists in improving the power conversion efficiency of organic solar cells (OSCs), due to the combination of favorable optical as well as electrical effects. In this work, the optical effects of two different spherical MNPs (Ag and Au nanospheres) on absorption enhancement in the active layer with the optimal thickness are analyzed in detail using finite-difference time-domain simulation. The results reveal clearly that the absorption enhancement in the OSCs is dependent on both the properties of MNPs and the types of the donor/acceptor blend systems. We conclude that Au nanospheres are less effective as compared to Ag nanospheres on absorption enhancement in OSCs, and large sized MNPs are favorable for light trapping in the organic active layer due to the prominent plasmonic excitations. For a low bandgap polymer PSBTBT:PC71BM blend system incorporating Ag nanospheres, a 11.2% increase in the integrated absorption is obtained due to the excitation of magnetic and electric resonances of surface plasmons. This work could contribute to the development of high efficiency plasmonic OSCs.