Highly Emissive and Color‐Tunable CuInS 2 ‐Based Colloidal Semiconductor Nanocrystals: Off‐Stoichiometry Effects and Improved Electroluminescence Performance

The off‐stoichiometry effects and gram‐scale production of luminescent CuInS 2 ‐based semiconductor nanocrystals, as well as their application in electroluminescence devices are reported. The crystal structures and optical properties of CuInS 2 nanocrystals can be significantly influenced by controlling their [Cu]/[In] molar ratio. A simple model adapted from the bulk materials is proposed to explain their off‐stoichiometry effects. Highly emissive and color‐tunable CuInS 2 ‐based NCs are prepared by a combination of [Cu]/[In] molar ratio optimization, ZnS shell coating, and CuInS 2 –ZnS alloying. The method is simple, hassle‐free, and easily scalable to fabricate tens of grams of nanocrystal powders with photoluminescence quantum yields up to around 65%. Furthermore, the performance of high‐quality CuInS 2 ‐based NCs in electroluminescence devices is examined. These devices have lower turn‐on voltages of around 5 V, brighter luminance up to approximately 2100 cd m −2 and improved injection efficiency of around 0.3 lm W −1 (at 100 cd m −2 ) in comparison to recent reports.