Radiative emission from Cu₂ZnSnS₄/ZnSn core/shell nanocrystals

Kesterite Cu₂ZnSnS₄ (CZTS) nanocrystals so far have been found to luminesce neither at room temperature nor at low temperature. Here a core–shell architecture for kesterite CZTS nanocrystals is demonstrated by applying a ZnSn-alloy shell overcoating approach. These CZTS/ZnSn nanocrystals show luminescence emission at 1.05 eV, which is red-shifted by about 0.4 eV from the absorption onset and is attributed to a radiative transition involving a deep defect. Temperature-dependent photoluminescence measurements within a range of 20–200 K indicate the presence of a competing nonradiative channel with an activation energy of 50–60 meV.