| Abstract: | Copper‐based ternary (I–III–VI) chalcogenide nanocrystals (NCs) are compositionally‐flexible semiconductors that do not contain lead (Pb) or cadmium (Cd). Cu‐In‐S NCs are the dominantly studied member of this important materials class and have been reported to contain optically‐active defect states. However, there are minimal reports of In‐free compositions that exhibit efficient photoluminescence (PL). Here, we report a novel solution‐phase synthesis of ≈4 nm defective nanocrystals (DNCs) composed of copper, aluminum, zinc, and sulfur with ≈20 % quantum yield and an attractive PL maximum of 450 nm. Extensive spectroscopic characterization suggests the presence of highly localized electronic states resulting in reasonably fast PL decays (≈1 ns), large vibrational energy spacing, small Stokes shift, and temperature‐independent PL linewidth and PL lifetime (between room temperature and ≈5 K). Furthermore, density functional theory (DFT) calculations suggest PL transitions arise from defects within a CuAl5S8 crystal lattice, which supports the experimental observation of highly‐localized states. The results reported here provide a new material with unique optoelectronic characteristics that is an important analog to well‐explored Cu‐In‐S NCs. |
