Colloidal Two-Dimensional Systems: CdSe Quantum Shells and Wells

Thin CdSe layers (“quantum shells”) were epitaxially grown onto CdS nanocrystal templates. Their optical properties are dominated by the shell thickness despite the different bandgap and size of the templates. The emission of the CdSe quantum shells, which can be tuned by varying the shell thickness, ranges from 520 to 650 nm (see Figure), and the emission quantum yield can be increased to over 40 % by coating the quantum shells with epitaxially grown CdS thin layers (CdSe colloidal “quantum wells”).