Plasmons Enhance Solar-Cell Output

Incorporating core-shell nanoparticles into the anodes of dye-sensitized solar cells (DSCs) can boost the cells’ photovoltaic performance, researchers at MIT report in ACS Nano (DOI: 10.1021/nn201808g). DSC photoanodes are generally made from a film of interconnected TiO₂ nanoparticles that are coated with a light-sensitive dye. The MIT group, which includes Jifa Qi, Xiangnan Dang, Paula T. Hammond, and Angela M. Belcher, prepared silver particles roughly 20 nm in diameter with a 2-nm-thick TiO₂ shell and embedded the core-shell particles among the bare TiO₂ particles. The team exploited interfacial electron waves known as surface plasmons, which intensify the electromagnetic field near the core-shell particles and enhance the dye molecules’ light absorption. The oxide shells help capitalize on those benefits by impeding the processes that quench the light-induced electronic excitations and thereby reduce the cell’s electrical output. Compared with 7.8%-efficient conventional DSCs, DSCs with just 0.1% by weight core-shell particles are 9% efficient and can be made with 25% thinner anodes. Similarly, conventional cell efficiencies can be obtained from core-shell cells fabricated from 62% less material, the team reports.