New Insights into the Formation and Color‐Tunable Optical Properties of Multinary Cu‐In‐Zn‐Based Chalcogenide Semiconductor Nanocrystals

Abstract A series of multinary Cu‐In‐Zn‐Se‐S nanocrystals (NCs) are synthesized via a phosphine‐free and one‐pot approach, in which the Se powder and 1‐dodecanethiol (DDT) are used as chalcogenide sources, respectively. The X‐ray photoelectron spectra are used to confirm the presence of lattice sulfur in the as‐obtained products. The emission color and the relative photoluminescence quantum yields of the Cu‐In‐Zn‐Se‐S NCs can be tuned by varying the Cu contents, the amount of Se powder, as well as the DDT dosage. In addition, the formation process of the multinary Cu‐In‐Zn‐Se‐S NCs is different from that of quaternary Cu‐In‐Zn‐S NCs, which is dominated by the doping of Cu ions into the In‐deficient In‐Zn‐Se‐S NCs but not the partial interdiffusion of Zn²⁺ into the Cu‐based NCs. This plausible deduction is based on the comparison of optical properties of the products synthesized using the hot‐injection and one‐pot methods. Furthermore, the performance of the solution‐processed quantum‐dot light‐emitting diodes (QLEDs) using the Cu‐In‐Zn‐Se‐S NCs as emission layers is examined, and the QLEDs exhibit a high luminance over 1500 cd m⁻² and a high peak current efficiency of ≈0.4 cd A⁻¹ at 1000 cd m⁻².