Near-Unity Red Mn²⁺ Photoluminescence Quantum Yield of Doped CsPbCl₃ Nanocrystals with Cd Incorporation

Although Mn²⁺ doping in semiconductor nanocrystals (NCs) has been studied for nearly three decades, the near 100% photoluminescence (PL) quantum yield (QY) of Mn²⁺ emission has never been realized so far. Herein, greatly improved PL QYs of Mn²⁺ emissions are reported in Mn²⁺-doped CsPbCl₃ NCs with various Mn²⁺ doping concentrations after CdCl₂ post-treatment at room temperature. Specifically, the near-unity QY and near single-exponential decay of red Mn²⁺ emission peaking at 627 nm in doped CsPbCl₃ NCs are obtained for the first time. The temperature dependence of steady-state and time-resolved PL spectra reveals that the CdCl₂ post-treatment significantly reduces the nonradiative defect states and enhances the energy transfer from host to Mn²⁺ ions. Moreover, the Mn²⁺:CsPbCl₃ NCs after CdCl₂ post-treatment exhibit robust stability and high PL QYs after multipurification. The results will provide an effective route to obtain doped perovskite NCs with high performance for white lighting emitting diodes.