Red‐Tuned Mn d–d Emission in Doped Semiconductor Nanocrystals

Abstract

Light-emitting Mn-doped semiconductor nanocrystals have been extensively studied for the last three decades for their intense and stable Mn d-d emission. In principle, this emission should be fixed at 585 nm (yellow), but recent studies have shown that the emission can be widely tuned even to 650 nm (red). This is a spectacular achievement as this would make Mn-doped nanocrystals efficient and tunable light emitters. Keeping these developments in view, the chemistry of the synthesis of these materials, their photophysical processes and the expected origins of their red emission are summarized in this Minireview. All the related important studies from 1992 onwards are chronologically discussed, and one particular case is elaborated on in detail. As these materials are potentially important for biology, and photovoltaic, sensing and light-emitting devices, this Minireview is expected to help researchers investigating the chemistry, physics and applications of these materials.

Mn doped AIZS/ZnS nanocrystals: Synthesis and optical properties

“…However, as shown in Figure 1, Mn doped in NCs do not present around 585 nm emission but a red-shift, and the PL shifts more towards the red region with the increase of Mn levels in Mn:AIZ/ZnS NCs. The red-shift by Mn doping was also observed in AIZS and other host NCs [53], and the red-shift has been attributed to the interaction of Mn to its environments in NC lattices as well as Mn-Mn coupling. It was also suggested that Mn-Mn coupling could cause some splitting energy levels between 4 T 1 and 6 A 1 states for the red-shift [53].…”

“…The red-shift by Mn doping was also observed in AIZS and other host NCs [53], and the red-shift has been attributed to the interaction of Mn to its environments in NC lattices as well as Mn-Mn coupling. It was also suggested that Mn-Mn coupling could cause some splitting energy levels between 4 T 1 and 6 A 1 states for the red-shift [53]. Because the Mn emission with Mn-Mn coupling could be a minor PL mechanism for the fast decay as we discussed, it is believed that the interaction of Mn to host NC lattices could be the major reason for the red-shift instead of Mn-Mn coupling.…”

“…What was observed in our experiments is that without such an addition (i.e., directly doping Mn in different levels to AIS NC surfaces and sequentially Zn etching to the NC surfaces), the final NCs presented green PL and no PL tunability by Mn levels was seen. It has been reported that the change of the host NC emission to Mn d-d emission happens only when the bandgap energy of the host NCs is higher than the energy gap of Mn d-d transition (~2.12 eV) [51, 53]. For AIS NCs prepared via thermal decomposition method, their PL peak is limited to yellow-orange (600 ~ 620 nm, or equivalently 2.06 ~ 2.00 eV), and their bandgap may be not wider than 2.12 eV.…”

“…Moreover, the reported ones mainly adopted hot-injection based syntheses, and their PL lifetimes were reported in much different values (around one microsecond and hundreds of microseconds). Although some recent paper suggested that the complex environment of Mn coordinated in may influence the NC emission energy and other optical properties [53], no effects of Mn levels in host AIS or AIZS NCs on NC optical properties were investigated. In this study, we prepared Mn doped AIZS/ZnS (Mn:AIZS/ZnS) NCs a simple synthesis approach only using heat-up and drop-wise addition of precursors, which is apt to scale up for NC mass production.…”

Manganese(II) Thiocyanate Complexes with Bis(phosphine Oxide) Ligands: Synthesis and Excitation Wavelength‐Dependent Multicolor Luminescence

“…[(L)MnHal 3 ] and L 6 [Mn 3 Cl 12 ] type (L = protonated or alkylated N-base) [16][17][18][19][20][21][22] and Mn 2+ -doped sulfide and oxide nanocrystals [1,23,24] exhibit red emission. The compounds containing both tetrahedral and octahedral Mn II centers, e.g.…”