Mitigation of metal-mediated losses by coating Au nanoparticles with dielectric layer in plasmonic solar cells

Abstract

Previous studies have concentrated on harnessing the 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 rarely been recognized. To address this issue, we herein embedded Au NPs coated with a dielectric SiO₂ layer into polymer solar cells, attempting to reduce the negative effects of these metallic nanostructures and thus increase photovoltaic photocurrent and efficiency. We constructed inverted polymer solar cells 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 which meanwhile is thin enough to maintain the plasmonic effects of the gold core upon photoexcitation. The study provides new insights into strategies harnessing plasmonic nanostructures to enhance photovoltaic performance, i.e. the balance between plasmonic effects and metal-mediated losses has to be comprehensively evaluated.