Mn²⁺-Doped ZnSe/ZnS Core/Shell Nanoplatelets as Low-Toxic UV-to-Vis Light-Converters with Enhanced Optical Properties

Doping quasi-two-dimensional semiconductor nanoplatelets (NPLs) which possess atomically exact thicknesses has attracted intense research interests, because it determines their unique optoelectronic properties. Dopants in ultrathin NPLs tend to diffuse the surface due self-purification effect, can result reduced optical performance such as shortened photoluminescence (PL) lifetimes, low PL quantum yields (PLQYs), and broadening of spectral linewidth. To address these issues, an effective way is overgrow with a shell locate dopants away from surface. In contrast Cd-based core/shell NPLs, heavy-metal-free made Zn-chalcogenides have hardly been explored. Here, we synthesized colloidal ZnSe:Mn/ZnS for first time via heat-up method. A combination zinc diethyldithiocarbamate ZnCl2 yielded smooth homogeneous shells on pregrown ZnSe:Mn NPLs. The resulting exhibit noticeably improved properties compared core-only particular, Mn2+ PLQY enhanced by more than one order magnitude upon deposition ZnS shells, be attributed increase internal efficiency. We systematically investigated both matrix- dopant-related kinetics well PLQYs. Further, using descriptive mathematical model, recognized dominant role nonradiative relaxation channels energy-transfer route ZnSe absorption luminescence ions. Our findings contribute better understanding applications superior fluorescence, photostability, toxicity, example, UV-light-converting devices, light-emitting diodes, imaging, bio-labeling.