Optical Properties and Electronic Structure of Copper Zinc Sulfide Nanocrystals

Continued efforts to transition toward renewable energy sources have spurred tremendous research into the discovery of near-infrared gap semiconductors. Here we describe the optical properties and electronic structure of copper zinc sulfide nanocrystals, with copper mole fractions as high as x(Cu) = 0.18. Copper zinc sulfide is shown to be a near-infrared gap semiconductor that exists in both zinc blende and wurtzite forms, similar to ZnS. The bandgap is shown to vary over 3.45-2.15 eV as the copper mole fraction is changed from 0.01 to 0.18. We find that the valence band of CuZnS nanocrystals has a significant tendency for hole localization, similar to other highly mismatched alloys. Further, our ultrafast studies are consistent with rapid (450 +/- 60 fs) removal of conduction band electrons and subsequent defect emission over 4.3 ns.

Automated summary

This study explores the optical properties and electronic structures of copper zinc sulfide nanocrystals, revealing them as near-infrared gap semiconductors with bandgap varying significantly with copper mole fraction. The valence band of CuZnS nanocrystals shows a tendency for hole localization, and ultrafast studies demonstrate rapid removal of conduction band electrons with subsequent defect emission over 4.3 ns.