Tuning Temperature Dependence of Dopant Luminescence via Local Lattice Strain in Core/Shell Nanocrystal Structure
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We report the tunable temperature dependence of Mn luminescence spectral characteristics (peak position and bandwidth) in Mn-doped CdS/ZnS core/shell nanocrystals via controlled local lattice strain at the dopant site that affects the local vibronic coupling and local thermal expansion. The lattice mismatch at the core/shell interface creates a gradient of lattice strain in the shell along the radial direction that allows varying the local lattice strain at the Mn 2+ site via the controlled radial doping location. Increasing the local lattice strain at the Mn 2+ site results in the stronger temperature broadening of Mn luminescence bandwidth due to the increasing softening of the vibrational mode coupled to Mn 2+ ligand field transition. Larger local lattice strain also causes a stronger temperature dependence of the luminescence peak, which indicates the enhanced local thermal expansion at the dopant site. 2012 American Chemical Society.