Rational Design and Synthesis of Highly Luminescent Multinary Cu‐In‐Zn‐S Semiconductor Nanocrystals with Tailored Nanostructures

Abstract Multinary copper chalcogenide semiconductor nanocrystals (NCs) have achieved increased attention due to their lessened toxicity and compositional versatility as well as their outstanding optical properties and optoelectronic applications in light‐emitting diodes (LEDs) and solar cells. Herein, the synthesis of highly luminescent multinary Cu‐In‐Zn‐S semiconductor NCs with tailored nanostructures, which exhibit the best absolute photoluminescence quantum yield of 90%, is presented. The tailored nanostructures are realized through the variation of the dosage and injection speed of Zn precursors, which determine the balance between Zn 2+ cation diffusion and ZnS shelling reaction. The depth profile measured using X‐ray photoelectron spectroscopy reveals the gradient distribution of Zn elements from core to surface in the samples synthesized using higher feeding amounts of Zn precursors in a one‐pot method, which favors the formation of a soft core/shell structure. Time‐resolved spectroscopic studies confirm that the inward diffusion of Zn 2+ and overcoating of a ZnS shell could reduce the number of intrinsic internal or surface defects, finally inducing a near‐unity radiative decay of excitons in single recombination pathway. As a demonstration, the highly luminescent multinary Cu‐In‐Zn‐S semiconductor NCs are incorporated into LEDs and a white light‐emitting diode is accessed through a two‐component strategy.