Pb²⁺ and Mn²⁺ Codoped Cs₂CdCl₄ Nanocrystals with Tunable Emission

2D layered metal halides have gained extensive attention due to their excellent chemical stability and remarkable optoelectronic properties. Herein, Pb²⁺/Mn²⁺ codoped Cs₂CdCl₄ nanocrystals (NCs) were synthesized by a facile hot-injection method. It is found that the Cs₂CdCl₄:0.6%Pb²⁺,5%Mn²⁺ NCs exhibit a photoluminescence quantum yield as high as 18.1%. Tunable emission color from cyan to white and then to orange covering the wavelength range between 400 and 750 nm was achieved by varying the doping concentration of Mn²⁺ ions in Cs₂CdCl₄:0.6%Pb²⁺ NCs. Spectral characterizations and density functional theory calculations reveal that the substantially enhanced Mn²⁺ emission centered at ∼600 nm is attributed to the efficient energy transfer from self-trapped excitons to Mn²⁺, with an energy transfer efficiency up to 40%. Importantly, Pb²⁺/Mn²⁺ codoped Cs₂CdCl₄ NCs also exhibit good air and thermal stabilities.