Study of Shell Growth Processes of Copper Iron Selenide‐based Near‐infrared Emitting Nanocrystals

Abstract Core/shell growth in nanosystems is usually accomplished either through deposition of the shell material or else through the conversion of a part of the core into the shell through ion exchange. Here we describe the interplay of both deposition processes in the case of CuFeSe₂/CdS nanocrystals. Specifically, we synthesize eskebornite CuFeSe₂ nanoparticles. Films of the nanocrystals exhibit an optical absorbance onset of 0.11 eV. Core/shell structures prepared from CuFeSe₂ show a unique dependence on the growth steps followed. In particular, we find that the addition of the cationic precursor before the anionic precursor leads to the formation of CdSe at the interface of the core and the shell. This is found to limit the tunability of the emission to 820 nm. In contrast, reversing the order of precursor addition prevents the formation of such a layer and leads to structures with a significantly greater emission tunability (900 nm to 1200 nm). Our observations are suggestive of the interplay of both processes in current syntheses for I‐III‐VI₂ based core/shell structures.