Suppression of Auger Recombination by Gradient Alloying in InAs/CdSe/CdS QDs

Colloidal quantum dots are promising for low-cost optoelectronic devices such as solar cells, light-emitting diodes (LEDs), lasers, and photodetectors. InAs-based quantum dots (QDs) are well suited for near-infrared (NIR) applications; however, to date, the highest-QY InAs QDs have exhibited short biexciton Auger lifetimes of ∼<50 ps. Here, we report a band engineering strategy that doubles the Auger lifetime in InAs CQDs. By developing a continuously graded thick CdSexS1-x shell, we synthesize InAs/CdSexS1-x/CdS CQDs that enable a smooth progression from the core to the outer shell, slowing the Auger process. We report a biexciton Auger lifetime of ∼105 ps compared to 17 ps for control InAs/CdSe/CdS CQDs. This represents a 2× increase of the Auger lifetime relative to the best value reported for InAs CQDs in prior literature.