(581b) Tunable Dual Emission from Colloidal Manganese-Doped Organic-Inorganic Hybrid Perovskite Nanoplatelets

Colloidal lead halide perovskite nanocrystals have recently emerged as a promising class of semiconductors for next-generation optoelectronics. Especially, two-dimensional perovskite nanoplatelets are considered to be one of the leading candidates due to their anisotropic nature, strong quantum- and dielectric-confinement, bright emission and high color purity.

In this work, we demonstrate a facile synthesis of colloidal organic-inorganic hybrid perovskite nanoplatelets (Chemical formula: L₂[ABX₃]_n-1BX₄, L: alkylammonium, A: methylammonium or formamidinium, B: lead, X: bromide or iodide, n(=1 or 2): number of PbBr₆^4-octahedral layers in out-of-plane direction) at room temperature using ligand-assisted reprecipitation technique. It is also shown that the bandgap and surface properties of the nanoplatelets can be tuned using the same synthetic protocol, which highlights the possibility of optimizing material properties for specific applications [1]. Then we show that manganese(Mn²⁺)-doped perovskite nanoplatelets can also be synthesized via ligand-assisted reprecipitation without any post-treatments, while dopant concentration is controlled by engineering the composition of divalent metal precursor solution. It turns out that substitutional doping of manganese in perovskite nanoplatelets induce significant enhancement of overall photoluminescence quantum yield (PLQY). It is believed to be the consequence of charge carriers being transferred to manganese state, which has high intrinsic PLQY, and avoiding fast nonradiative decay pathways. And manganese-doped perovskite nanoplatelets also exhibit excitation power-dependent dual color emission. To be more specific, photoluminescence intensity from nanoplatelets scales linearly with excitation intensity, which is consistent with the characteristics of excitonic emission, while photoluminescence intensity from manganese state starts to saturate at high excitation intensity. This corresponds to the change of perceived color and we show that emission color can be tuned across the color space. Then we propose a kinetic model that captures the essential dynamics of dual color emission and discuss its implications. To summarize, our work introduces anisotropic, tunable, highly-confined intrinsic dual emitters that can expand perovskite nanocrystal functionality.

1. Ha, S.K.; Tisdale, W.A. Facile Synthesis of Colloidal Lead Halide Perovskite Nanoplatelets via Ligand-Assisted Reprecipitation. J. Vis. Exp. 2019, 152, e60114