Efficient and Stable Luminescence from Mn²⁺ in Core and Core-Isocrystalline Shell CsPbCl₃ Perovskite Nanocrystals

There has been a growing interest in applying CsPbX₃ (X = Cl, Br, I) nanocrystals (NCs) for optoelectronic application. However, research on doping of this new class of promising NCs with optically active and/or magnetic transition metal ions is still limited. Here we report a facile room temperature method for Mn²⁺ doping into CsPbCl₃ NCs. By addition of a small amount of concentrated HCl acid to a clear solution containing Mn²⁺, Cs⁺, and Pb²⁺ precursors, Mn²⁺-doped CsPbCl₃ NCs with strong orange luminescence of Mn²⁺ at ∼600 nm are obtained. Mn²⁺-doped CsPbCl₃ NCs show the characteristic cubic phase structure very similar to the undoped counterpart, indicating that the nucleation and growth mechanism are not significantly modified for the doping concentrations realized (0.1 at. % - 2.1 at. %). To enhance the Mn²⁺ emission intensity and to improve the stability of the doped NCs, isocrystalline shell growth was applied. Growth of an undoped CsPbCl₃ shell greatly enhanced the emission intensity of Mn²⁺ and resulted in lengthening the radiative lifetime of the Mn²⁺ emission to 1.4 ms. The core-shell NCs also show superior thermal stability and no thermal degradation up to at least 110 °C, which is important in applications.