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.

Graphene-based p-type dye-sensitized solar cells (p-DSSCs) have been proposed and fabricated using copper oxide urchin-like nanostructures (COUN) as photocathode with an FeS2 counter electrode (CE). COUN composed of Cu2O core sphere and CuO shell nanorods with overall diameters of 2 to 4  μm were grown by a simple hydrothermal method with self-assemble nucleation. It was figured out that the formation of copper oxide core/shell structures could be adjusted by an ammonia additive leading to pH change of the precursor solution. In addition to a photocathode, we also demonstrated FeS2 thin films as an efficient CE material alternative to the conventional Pt CEs in DSSCs. FeS2 nanostructures, with diameters of 50 to 80 nm, were synthesized by a similar hydrothermal approach. FeS2 nanostructures are demonstrated to be an outstanding CE material in p-DSSCs. We report graphene/COUN as photocathode and Pt/FeS2 as CE in p-DSSCs, and results show that the synergetic combination of electrodes in each side (increased interconnectivity between COUN and graphene layer, high surface area, and high catalytic activity of FeS2) increased the power conversion efficiency from 1.56% to 3.14%. The excellent performances of COUN and FeS2 thin film in working and CEs, respectively, make them unique choices among the various photocathode and CE materials studied.