Effect of surface defects on photoluminescence properties of CdSe quantum dots in glasses

Cadmium selenide quantum dots (CdSe QDs) have shown great potential for applications in the visible range over the last few decades. Embedding CdSe QDs into inorganic glass matrix improves their stability, but complicates their surface conditions and deteriorates their optical properties. In this work, CdSe QDs with tunable and narrow band intrinsic photoluminescence (PL) are precipitated in silicate glasses by adjusting the heat-treatment temperatures. With the increase in heat-treatment temperature, PL peaks shift to long wavelength side with simultaneous reduction in full width at half maximum, while both PL quantum yields and lifetimes decrease. Ultrafast carrier dynamics analysis reveals that the above changes on PL properties are induced by the transformation of Cd2+-related to Se2--related surface defects during heat-treatment. Electron trapping by shallow Cd2+-related defects is responsible for the broad band defect emission, and hole trapping by Se2--related defects results in quenching of defect emission. These results uncover the relationship between surface defects of CdSe QDs and their PL properties, facilitating their applications towards light-emitting diodes (LEDs), backlight displays, and lasers.