Improving Photoluminescence Emission Efficiency of Nanocluster-Based Materials by in Situ Doping Synthetic Strategy

Abstract

Solid-state red phosphors of Mn2+-doped nanocrystals usually suffer from poor intensity. While the d–d emission of Mn2+ in yellow window has been extensively studied, shift toward lower energy remains challenging. Typically, intrinsic surface defects and self-purification of dopants are two obstacles for enhancing the intensity of red emission. Moreover, for red phosphors Mn2+ ions also need an appropriate host matrix and environment. Through an in situ doping strategy and optimization of the Mn2+ doping level, intense red-emitting Mn2+ dopant emission is reported here for MnCdInS@InS host. The doping strategy allows doping of Mn2+ at the core and/or surface sites of supertetrahedral “core–shell” nanocluster (Mn@MnCdInS@InS), leading to the red emission (at 643 nm) with over 40% quantum yield. Moreover, systematic control of doping level results in a series of crystalline Mn2+-doped materials with tunable photoluminescence quantum yield. In addition to the synthesis of an important class of red-emitting materials rarely obtained from Mn2+ doping, details of the physical chemistry associated with the doping process are probed with the new fundamental findings reported here.

Mn Doping in Centimeter-Sized Layered 2D Butylammonium Lead Bromide (BA2PbBr4) Single Crystals and Their Optical Properties

“…The Mn emission increases sharply with the increase in dopant concentration in BA 2 PbBr 4 single crystals, as shown in Figure a and Figure S8. A similar trend has been previously observed for BA 2 PbBr 4 powders and for other hosts as well, ,, which is because of the increase in the emitting Mn dopant centers. In contrast, the excitonic emissions show a reverse trend; that is, the intensity of the excitonic emission decreases with an increase in the dopant concentration (Figure a).…”

Postsynthesis Doping of Mn and Yb into CsPbX3 (X = Cl, Br, or I) Perovskite Nanocrystals for Downconversion Emission

“…The intensity of the Mn emission initially increases with Mn content reaching a maximum for 4.3% Mn doping for 5 ML CsPbBr 3 NPLs and then decreases with further increases in Mn concentration. A similar dependence of Mn emission is usually observed ,− for different hosts, where the intensity increases initially because of the increase in the number of emitting dopant centers, but the increase in dopant concentration increases the extent of exchange interaction between neighboring Mn atoms, decreasing the emission efficiency per dopant ion . An opposing interplay between both processes gives the maximum Mn emission at an intermediate dopant concentration.…”

New Insights into Mn–Mn Coupling Interaction-Directed Photoluminescence Quenching Mechanism in Mn2+-Doped Semiconductors

“…Figure a shows the temperature-dependent PL spectra of MCOF-6 collected under maximum excitation wavelength at the corresponding testing temperature. Mn 2+ -related maximum emission of MCOF-6 experienced a red shift when the testing temperature decreased from 293 to 83 K. Such a red shift of the maximum emission mainly stemmed from the crystal lattice strain caused by the shrinkage of unit cell, which led to large d–d splitting of Mn 2+ ions and correspondingly lowered the gap of 4 T 1 → 6 A 1 transition. , To understand the correlation between PL intensity and the testing temperaure, the integrated areas of PL curves in Figure a were calculated and are shown in Figure b. A nonmonotonic increase in the PL intensity of MCOF-6 was obviously observed.…”

“…Recently, well-defined Mn 2+ -doped chalcogenide supertetrahedral T n -type nanoclusters (NCs, T is short for tetrahedron, and n is the number of metal sites along the edge of the tetrahedron) with exact numbers and precise location of Mn 2+ ions have been used as special models for probing Mn 2+ -related PL properties. − For example, we studied the doping of single or multiple manganese ions in T4-ZnGaSnS or T5-CdInS NCs − and also explored the effect of intracluster and intercluster torsion stress on Mn 2+ -related red emission from T4-MnInS-based metal chalcogenides . Unfortunately, a group of ideal models (i.e., structurally similar T n clusters) with subtle and accurate differences in Mn···Mn distances and coordination environments have not been reported previously for this system.…”