Previous studies have concentrated on harnessing surface plasmonic effects of metallic nanoparticles (NPs) to improve polymer solar cell performance.Although ample examples have evidenced the viability of this methodology, the adverse effect of device photocurrent reduction via the intrinsic metal-mediated losses of plasmonic metal NPs, which hampers further enhancement of device efficiency, has been rarely recognized.To address this issue, we herein embedded Au NPs coated with dielectric SiO2 layer into polymer solar cells attempting to reduce negative effects of these metallic nanostructures and thus increase photovoltaic photocurrent and efficiency.We constructed inverted polymer solar cell based on poly(3-hexylthiophene) and [6,6]-phenyl-C61-butyric acid methyl ester, and blended Au NPs coated with SiO2 layer, i.e., Au@SiO2 core-shell nanostructures into the active layer.Compared with plasmonic solar cells embedded with sole Au NPs, the device incorporating Au@SiO2 core-shell nanostructures indeed exhibited significantly augmented photocurrent density, though not a superior overall efficiency.The photocurrent density increase is attributed to the dielectric layer coating Au NPs, which mitigates metal-mediated losses such as exciton quenching probably induced by the electron accumulation on the metallic surface, but meanwhile is thin enough to maintain the plasmonic effects of the gold core upon photoexcitation.The study provides new insights into strategies harnessing plasmonie nanostructures to enhance photovoltaic performance, i.e., the balance between plasmonic effects and metal-mediated losses has to be comprehensively evaluated.