A Layer-by-Layer Growth Strategy for Large-Size InP/ZnSe/ZnS Core–Shell Quantum Dots Enabling High-Efficiency Light-Emitting Diodes

Shell is of great significance to the enhancement in the photoluminescence quantum yield (PLQY) and stability of core–shell-type quantum dots (QDs). InP/ZnS core–shell QDs without intrinsic toxicity have shown huge potential as a replacement for the widely used cadmium-containing QDs; however, it is still challenging to control the growth of InP-based core–shell QDs due to the lattice mismatch between the InP core and ZnS shell. Here, we report on the synthesis of ∼15-nm-size InP/ZnSe/ZnS QDs with a thick ZnS outer shell by a layer-by-layer shell growth strategy. The ZnS shell was prepared by a circularly gradient temperature rise and long reaction procedure in each step, which not only ensures relatively low precursor concentration preventing the anisotropic growth of QDs but also allows the low-reactivity source to be decomposed sufficiently to achieve layer-by-layer growth of a thick ZnS shell. The resulting QDs show the highest PLQY of 73%, narrow emission line width of up to 40 nm, wide spectrum tuna...