Thermal stability of Mn²⁺ion luminescence in Mn-doped core–shell quantum dots

Abstract

The thermal stability of luminescence is important for the application of quantum dots (QDs) in light-emitting devices. The temperature-dependent photoluminescence (PL) intensities and decay times of Mn-doped ZnS, ZnSe, and ZnSeS alloyed core-shell QD films were studied in the temperature range from 80 to 500 K by steady-state and time-resolved PL spectroscopy. It was found that the thermal stability of Mn-doped QD emissions was significantly dependent on the shell thickness and the host bandgap, which was higher than that of workhorse CdSe QDs. Nearly no PL quenching took place in Mn:ZnS QDs with a thick ZnS shell, which kept a high PL quantum yield (QY) of ~50% even at 500 K; and the thermally stable PL was also observed in highly luminescent Mn:ZnSe and Mn:ZnSeS QDs with a quenching temperature over 200 °C. Further, the stability of Mn-doped QDs with different shell thickness at high temperature was also examined through heating-cooling cycling experiments. The PL quenching in the thick shell-coated Mn-doped QDs was almost totally recovered. The PL quenching mechanisms of the Mn(2+) ion emissions were discussed.

Mn doped AIZS/ZnS nanocrystals: Synthesis and optical properties

“…Other two types of Mn:AIZS/ZnS NCs were also tested and presented the similar behavior to that of 0.075mmol-Mn:AIZS/ZnS NCs. It is generally thought that Mn emission from Mn-doped NCs especially with a thick ZnS shell is of thermal stability (not quenched in a wide temperature range up to 200 °C) [62]. In our work, as we discussed, the Mn emission with Mn-Mn coupling is excluded or considered as a minor mechanism for the fast decayed PL, and the Mn emission from Mn pairs or diluted Mn dopants in NCs possesses a very low percentage in all PL intensity.…”

A facile route to aqueous Ag:ZnCdS and Ag:ZnCdSeS quantum dots: Pure emission color tunable over entire visible spectrum

“…The detailed PL decay data for all the samples are listed in Table 2. Generally, the shorter component of PL lifetime should be attributed to surface defects related to the radiative recombination, whereas the longer one was due to the Ag dopant emission [41][42]. The average PL lifetimes of all Agbased doped core and core/shell QDs were in the order of hundreds of nanoseconds.…”

Impurity Location-Dependent Relaxation Dynamics of Cu:CdS Quantum Dots

“…Transition-metal or rare-earth ion-doped quantum dots (QDs), especially sulfides, are emerging as alternatives to semiconductor QDs with stable, strong, and tunable luminescence in the visible spectral region for different optoelectronic applications. Minimized self-absorption [3, 4], long excited-state lifetimes [5, 6], tunable emission spectral widths [7], and thermal stability [8, 9] are the characteristic properties of these nanocrystals making those doped nanocrystals as important QDs. Especially, semiconductor nanocrystals of a wide band-gap such as cadmium or zinc chalcogenides, doped with transition-metal ions, become alternative materials to overcome the limitation of organic phosphor-based LEDs (OLEDs) because QD-LEDs do not suffer from the spin statistics that limits the internal quantum efficiency of fluorescent OLEDs [10].…”

“…Especially, semiconductor nanocrystals of a wide band-gap such as cadmium or zinc chalcogenides, doped with transition-metal ions, become alternative materials to overcome the limitation of organic phosphor-based LEDs (OLEDs) because QD-LEDs do not suffer from the spin statistics that limits the internal quantum efficiency of fluorescent OLEDs [10]. The incorporation of transition-metal dopants like Mn, Cu, and Co ions introduces intermediate energy states, such as trap states, between the valence and the conduction bands of host semiconductor nanocrystals and influences the relaxation dynamics of host materials [9, 11–14]. As a consequence, the dopant emission results in unique optical properties whose nature varies with chosen hosts and dopants.…”