Near-infrared bandgap Cd-rich PbxCd1-xS quantum dot with record long exciton lifetime

PbS/CdS core-shell quantum dots (QD) with diameters of <4 nm have previously only been demonstrated with the formation of a monolayer of pure phase CdS shell through cation exchange. The lattice mismatch between the zincblende CdS shell and the rocksalt PbS core limits the optimal thickness of the shell to 1 monolayer to prevent defect formation at the coreshell interface in order to maximize photoluminescence quantum yield (PLQY) and lifetime. This work demonstrates for the first time the formation of a Cd-rich Pb0.35Cd0.65S alloyed core-shell QD through cation exchange with a record long exciton lifetime of 3.8 µs and much-improved PLQY.