Edge versus Interior Mn²⁺ Doping in 2D Layered Butylammonium Lead Bromide Perovskite Single Crystals

Abstract

Butylammonium lead bromide [(BA) 2 PbBr 4 ] has an atomically thin twodimensional (2D) quantum well structure. So if Mn 2+ ions are doped into such crystals, then one would expect efficient energy transfer from the strongly confined excitons to the dopants. Perhaps, the energy transfer happens to yield Mn 2+ emission with a peak at 2.05 eV (605 nm). But significant excitonic emission is also observed, suggesting that the energy transfer process is not that efficient. Is there a spatial separation between Mn 2+ ions and excitons reducing the energy transfer efficiency? To address this question, here, we study single crystals of Mn 2+ -doped (BA) 2 PbBr 4 . The excitons located in the edge and interior of layers of (BA) 2 PbBr 4 show different excitonic emissions. This difference allows us to separately probe the interaction of edge excitons and interior excitons with the Mn 2+ ions, using temperature-dependent (7−300 K) photoluminescence (PL) spectroscopy and spatially resolved PL. We find that the edge excitons mainly sensitize the Mn 2+ ions because Mn 2+ doping is preferred near the layer edges. Both the poor doping concentration (0.6% Mn 2+ ) and edge doping lead to a large spatial separation between the interior excitons and dopant centers, reducing the energy transfer efficiency. These new insights will be helpful for the better design and application of luminescent Mn 2+doped 2D layered hybrid perovskites.

Thermal Evolution of the Structure and Luminescence of the Hybrid-Cation-Stabilized [(4AMTP)PbBr2]2PbBr4 Layered Perovskite

“…Temperature-dependent PL spectra of [(4AMTP)­PbBr 2 ] 2 PbBr 4 single crystals in Figure a show two emission peaks at 300 K. Likewise, the absorption spectrum of the sample also has two peaks, as shown in Figure S6 of the SI. Similar results of two absorption and emission peaks have been shown by a series of A 2 PbX 4 (X = I, Br, and Cl) single crystals in prior literature. ,, The exact reasons behind two such emission peaks are still being debated, and some reports suggest both are excitonic emission originating from different parts of the single crystals. , The PL decay measurements of both peaks shown in Figure S7 of the SI suggest fast enough lifetimes (nanosecond scale) that can be associated with the excitonic emission. The spectrum at 300 K (Figure a) also shows the tailing of a low energy excitonic peak, mainly described in the literature due to exciton–phonon coupling .…”

“…Similar results of two absorption and emission peaks have been shown by a series of A 2 PbX 4 (X = I, Br, and Cl) single crystals in prior literature. 25,16,31 The exact reasons behind two such emission peaks are still being debated, and some reports suggest both are excitonic emission originating from different parts of the single crystals. 16,32 The PL decay measurements of both peaks shown in Figure S7 of the SI suggest fast enough lifetimes (nanosecond scale) that can be associated with the excitonic emission.…”

Size-Tunable Manganese-Doped Spheroidal CsPbCl3 Quantum Dots

“…The corresponding difference transient (ΔΔ A ) is plotted in Figure d, which provides an exciton to Mn 2+ ET time scale of 112 ps, which is too slow for Dexter type of energy transfer, and matches general FRET transfer rates for QDs . A similar exciton to Mn 2+ ET time scale has been reported for CsPbCl 3 :Mn 2+ nanocrystals, supporting contribution from a FRET-like mechanism. , Likewise, Mn 2+ doping in 2D layered butylammonium lead bromide perovskite single crystals also demonstrated long ET rates from excitons to Mn 2+ dopants located at the edge of the single crystals …”

“…15,42 Likewise, Mn 2+ doping in 2D layered butylammonium lead bromide perovskite single crystals also demonstrated long ET rates from excitons to Mn 2+ dopants located at the edge of the single crystals. 43 Overall, this work demonstrated a new strategy to synthesize size-dependent CsPbCl 3 :Mn 2+ QDs for the first time. This was achieved via a combined interfacial anion and cation exchange starting from CsPbBr 3 QDs using a MnCl 2 aqueous solution.…”

Induced Circularly Polarized Luminescence and Exciton Fine Structure Splitting in Magnetic-Doped Chiral Perovskites

“…Mn-1–4 were synthesized with some modifications on the reported methods. ,− PbBr 2 and MnBr 2 with different ratios (Mn/Pb ratio: 0.25, 0.5, 0.75, 1) with the sum of the two precursors equal to 1 mmol were dissolved in 3 mL of HBr. A clear solution was obtained under magnetic stirring at 90 °C, and it was cooled down to room temperature at 2 °C/h.…”