Microwave-assisted synthesis of highly photoluminescent core/shell CuInZnSe/ZnS quantum dots as photovoltaic absorbers

Abstract

Water-dispersible core/shell CuInZnSe/ZnS (CIZSe/ZnS) quantum dots (QDs) were efficiently synthesized under microwave irradiation using N-acetylcysteine (NAC) and sodium citrate as capping agents. The photoluminescence (PL) emission of CIZSe/ZnS QDs can be tuned from 593 to 733 nm with varying the Zn : Cu molar ratio in the CIZSe core. CIZSe/ZnS QDs prepared with a Zn : Cu ratio of 0.5 exhibit the highest PL quantum yield (54%) and the longest PL lifetime (515 ns) originating from the recombination of donor–acceptor pairs. The potential of CIZSe/ZnS QDs as photoabsorbers in QD-sensitized solar cells was also evaluated. An adequate type-II band alignment is observed between TiO₂ and CIZSe/ZnS QDs, indicating that photogenerated electrons in CIZSe/ZnS QDs could efficiently be injected into TiO₂.