Abstract:
Butylammonium lead bromide [(BA)2PbBr4] has an atomically thin two-dimensional (2D) quantum well structure. So if Mn2+ 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 Mn2+ 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 Mn2+ ions and excitons reducing the energy transfer efficiency? To address this question, here, we study single crystals of Mn2+-doped (BA)2PbBr4. The excitons located in the edge and interior of layers of (BA)2PbBr4 show different excitonic emissions. This difference allows us to separately probe the interaction of edge excitons and interior excitons with the Mn2+ ions, using temperature-dependent (7–300 K) photoluminescence (PL) spectroscopy and spatially resolved PL. We find that the edge excitons mainly sensitize the Mn2+ ions because Mn2+ doping is preferred near the layer edges. Both the poor doping concentration (0.6% Mn2+) 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 Mn2+-doped 2D layered hybrid perovskites.