Comparative photoluminescence properties of type-I and type-II CdTe/CdS core/shell quantum dots

• Type-I and type-II quantum structured CdTe/CdS QDs were successfully synthesized in water from the same 3.0-nm CdTe core QDs with increasing the thickness of the CdS shell.
• Type-I CdTe/CdS QDs showed strong luminescence at 550 nm with short decay time of 20 ns; while type-II QDs emitted strong luminescence in the NIR region of 700–830 nm with very long decay-time of 190 ns.
• With increasing temperature, the much more bandgap narrowing and much stronger exciton–acoustic phonon interaction were observed in type-I CdTe/CdS QDs that are reasonably attributed to the stronger confinement of excitons.

High quality type-I and type-II CdTe/CdS quantum dots (QDs) were designed and synthesized in water at 90 °C using the same 3.0-nm CdTe core QDs with different CdS shell thicknesses. Time-resolved and temperature-dependent photoluminescence techniques were used to study comparatively their optical properties, showing strong luminescence peaking at 550 nm with the short decay time of 20 ns for type-I CdTe/CdS QDs; and strong luminescence in the near-infrared region of 700–830 nm with very long decay time of 190 ns for the type-II ones. In addition, exciton–acoustic phonon interaction is much stronger in type-I QDs compared to that in type-II ones that is rationally due to the stronger confinement effect.

Figure optionsDownload high-quality image (91 K)Download as PowerPoint slide