Composition Control in CuInZnS2 Nanocrystals by Cation Exchange and Their Phase Transfer

Abstract

Copper indium zinc sulfide (CIZS) nanocrystals (NCs) are quaternary semiconductor compounds with optoelectronic properties that are highly dependent on their exact element composition. Here, we demonstrate a two-step synthesis route to prepare CIZS particles exhibiting a molar zinc content of up to 85% and a spatially homogeneous cation distribution via simultaneous cation exchange in which In³⁺ and Zn²⁺ are introduced into previously prepared copper sulfide particles. By varying the synthesis parameters, namely the reaction intervals as well as the ratio of initially used cation-donating educts, and by analyzing the resulting CIZS particles with spectroscopic and electron microscopic methods, a detailed insight into the composition and size control is received. Furthermore, we present a versatile procedure for the phase transfer of the as-prepared CIZS NCs with various cation compositions into water by replacing the 1-dodecanthiol ligands with 11-mercaptoundecanoic acid. This corresponds to a thiol–thiol exchange that is facilitated by the use of tetramethylammonium hydroxide as a strong base and leads to aqueous colloids with preserved optical properties, particle size and composition.