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 Zn 2+ 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 .
Multinary Cu-based chalcogenide nanocrystals (NCs) are excellent candidates for optoelectronic applications, but their growth mechanism and its impacts on the NCs’ optical properties remain controversial. Herein, we employed a simple colloidal chemistry method for the growth of multinary Cu-based NCs including ternary Cu–In–S NCs, quaternary Cu–In–Se–S NCs, and five-component Cu–In–Zn–Se–S NCs, to explore their growth mechanism and investigate their optical properties. It is found that the ternary Cu–In–S NCs contain a large number of copper vacancies, which affect the major acceptor level for the exciton recombination. With the high reaction activity of Se, the quaternary Cu–In–Se–S NCs form at low reaction temperature and have a red-shift of the photoluminescence (PL) maximum due to the recombination from the conduction band to the acceptor level. The formation process of five-component Cu–In–Zn–Se–S NCs highly depends on the Zn amount, which shows a competitive relationship between the NCs’ growth and diffusion of Zn, leading to the red- and blue-shift of PL maximum, respectively. Our study provides a clear map for the growth of multinary Cu-based NCs and shows their impacts on optical properties.
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