Temperature-dependent photoluminescence properties of Mn-doped ZnSe quantum dots

Thermal stability of quantum dot(QD) luminescence is considered as an important factor for their applications in luminescent devices because of the Joule heat caused by inevitable current. The temperature-dependent photoluminescence(PL) properties of Mn-doped ZnSe(Mn: ZnSe) QDs with different shell thickness in the temperature range from 80 to 500 K were studied by steady-state and time-resolved PL spectra. It was found that the Mn: ZnSe QDs with thick shell(6.5 monolayers(MLs)) exhibited better PL thermal stability than the thin shell coated ones(2.6 MLs). Because almost no PL quenching occurred for thick shell-coated Mn-doped QDs from 80 to 400 K, their PL quantum yield(QY) could keep 60% even at 400 K. Moreover, based on the change in temperature-dependent PL intensities and lifetimes of Mn: ZnSe QDs, the thermal quenching mechanism was proposed. Finally, the stability of Mn: ZnSe QDs with different shell thickness are discussed on the basis of heating-cooling cycling examination(300-500-300 K). For Mn: ZnSe QDs with thick shell, the PL was nearly totally recovered after the cycling examination. Thus, Mn: ZnSe QDs are promising for applications in luminescent devices, where strong thermal effect is inevitable.