Temperature-Dependent Photoluminescence of Mn-Doped ZnSe Nanocrystals

The Mn-doped ZnSe nanocrystal (NC) was synthesized by overcoating ZnSe shell onto a Mn²⁺ ions-adsorbed ZnSe core. The Mn ions were suggested to be mostly inside the ZnSe:Mn/ZnSe NCs and the luminescence from Mn ions near the NC's surface was much lower. With the increase of temperature from 77 to 297 K, the NC's photoluminescent (PL) lifetime of interior Mn²⁺ ions was increased from 0.62 ms to 0.83 ms, and then was decreased to 0.44 ms. The temperature-dependent electron paramagnetic resonance (EPR) spectra showed that the EPR line-width was decreased from 7.5 Gauss to 3.1 Gauss with the increase of temperature, indicating that the spin-orbit interaction became weaker with temperature, and it is suggested to result in the rise of the PL lifetime at the low temperature region. On the other hand, the drop of the PL lifetime at the high temperature region is due to some thermal-activated non-radiative processes.