Plasmonic Effects of Au@Ag Nanoparticles in Buffer and Active Layers of Polymer Solar Cells for Efficiency Enhancement.

Embedding nanoparticles (NPs) in the buffer layer of bulk heterojunction polymer solar cells (BHJ PSCs) excites the surface plasmonic polaritons and enhances the pathlength of the light in the solar cells. On the other hand, embedding NPs in the active layer significantly improves absorption and increases the production of electron-hole (e-h) pairs in BHJ PSCs. Increasing the volume ratio of NPs embedded in BHJ PSCs enables the direct interfacing of the NPs with the active layer, which then serves as a charge recombination center. Therefore, this study integrates the aforementioned phenomena by exploiting the effects of embedding plasmonic Au@Ag NPs in the buffer and active layers of PSC and then determining the optimum volume ratio of Au@Ag NPs. The results show the absorption is increased across the 350-750 nm wavelength region, and the PCE of the device with embedded Au@Ag in two locations is enhanced from 2.50 to 4.24%, which implies a 69.6% improvement in the PCE in comparison to the reference cell. This improvement is contributed by the combined localized surface plasmon resonance (LSPR) effects of multi-positional Au@Ag NPs, spiky durian-shaped morphology of Au@Ag NPs, and optimized volume ratio of Au@Ag NPs embedded in the PEDOT: PSS and PTB7:PC 71 BM layers.