Indium Phosphide-Based Quantum Dots with Shell-Enhanced Absorption for Luminescent Down-Conversion

It is shown that admixing small amounts of cadmium into the shell of InP/ZnSe core/shell quantum dots results in an increased absorption of blue light and a limited redshift of the band-edge emission. These effects reflect the reduced bandgap of (Zn,Cd)Se alloys and their smaller conduction-band offset with InP. Nevertheless, adjusting the InP core size enables InP/ZnSe and InP/(Zn,Cd)Se quantum dots with identical emission characteristics to be made. Processing both materials into remote phosphor disks, it is demonstrated that the shell-enhanced absorbance of InP/(Zn,Cd)Se has the double benefit of suppressing self-absorption and reducing the amount of quantum dots by weight needed to attain a given blue-to-red color conversion.