Heating-up synthesis of cadimum-free and color-tunable quaternary and five-component Cu–In–Zn–S-based semiconductor nanocrystals

Abstract

A simple heating-up colloidal approach has been developed to synthesize quaternary Cu–In–Zn–S (CIZS) nanocystals with different emission colors, which can be tuned by varying the Cu : In : Zn precursor ratios. The as-obtained products have a quasi-triangular shape with a small size distribution, and their crystal phase can be varied from cubic zinc-blende to hexagonal wurtzite structure with an increase of Cu stoichiometry. The inductively coupled plasma optical emission spectrometry (ICP-OES) results reveal that the as-obtained CIZS nanocrystals are Cu-deficient, and the Cu-vacancies have a significant effect on their optical properties. Moreover, the photoluminescence (PL) spectra of the CIZS nanocrystals recorded at different growth periods indicate that the partial cation exchange of Cu⁺ and In³⁺ with Zn²⁺ takes charge of the growth process. After coating a ZnS shell over the CIZS nanocrystals, the PL quantum yield (PLQY) is improved greatly and a blue-shift of the PL peak is observed as compared to that of plain CIZS nanocrystals. More interestingly, the highly luminescent CIZS/ZnS core/shell nanocrystals with different colors have been incorporated into poly(dimethylsiloxane) (PDMS) to be fabricated on an engraved “BJTU” glass substrate, and the as-obtained PDMS membranes exhibit a bright emission under UV light, which also show good stability when they are bent arbitrarily or immersed in water. This heating-up method has also been extended to the preparation of five-component Cu–Ag–In–Zn–S and Cu–Mn–In–Zn–S nanocrystals, which possess a cubic zinc-blende crystal structure and have bright luminescence. Our work may shed light on the synthesis of multi-component semiconductor nanocrystals.