Plasmonic noble metal@metal oxide core-shell nanoparticles for dye-sensitized solar cell applications

The aim of this review is to summarize recent advances in the field of dye-sensitized solar cells (DSSCs) utilizing plasmonic nanoparticles (NPs), where the effect of plasmonic NPs in terms of size, shape, and composition on the overall efficiency has been taken into account. Various approaches for size and shape-controlled synthesis of plasmonic NPs (typically Ag or Au NPs) have been discussed. Plasmonic NPs are found to be unstable in iodide based redox electrolytes commonly used in DSSCs and high temperature sintering during photoanode preparation. Therefore, plasmonic NPs are encapsulated with metal oxides, specifically TiO2 or SiO2 NPs, to form core-shell structures in order to improve their chemical and thermal stability. The synthesis process and optical characteristics of plasmonic core-shell NPs are discussed in detail. Incorporation of plasmonic core-shell NPs has improved the light harvesting capability of the photoanode and hence significantly improved the performance of DSSCs. Plasmonic core-shell NPs have also decreased the amount of active material required to attain high efficiency. The surface plasmon resonance (SPR) of plasmonic NPs is tuned by varying their size, shape or shell thickness and composition for better overlapping with the absorption spectrum of the sensitizer in order to further improve the light harvesting capability. The factors responsible for the enhancement in the performance of plasmonic DSSCs, such as resonant energy transfer, hot electron injection, and local electromagnetic field enhancement, are discussed in detail. Finally, the existing challenges in the field of DSSCs and future prospects to solve these problems in order to further improve the solar energy conversion are also discussed.