A series of Mn 2+ -doped CsPbCl 3 nanocrystals (NCs) was synthesized using reaction temperature and precursor concentration to tune Mn 2+ concentrations up to 14%, and then studied using variable-temperature photoluminescence (PL) spectroscopy. All doped NCs show Mn 2+ 4 T 1g → 6 A 1g d−d luminescence within the optical gap coexisting with excitonic luminescence at the NC absorption edge. Room-temperature Mn 2+ PL quantum yields increase with increased doping, reaching ∼60% at ∼3 ± 1% Mn 2+ before decreasing at higher concentrations. The low-doping regime is characterized by singleexponential PL decay with a concentration-independent lifetime of 1.8 ms, reflecting efficient luminescence of isolated Mn 2+ . At elevated doping, the decay is shorter, multiexponential, and concentration-dependent, reflecting the introduction of Mn 2+ −Mn 2+ dimers and energy migration to traps. A large, anomalous decrease in Mn 2+ PL intensity is observed with decreasing temperature, stemming from the strongly temperature-dependent exciton lifetime and slow exciton-to-Mn 2+ energy transfer, which combine to give a strongly temperature-dependent branching ratio for Mn 2+ sensitization.

Although Mn 2+ doping in semiconductor nanocrystals (NCs) has been studied for nearly three decades, the near 100% photoluminescence (PL) quantum yield (QY) of Mn 2+ emission has never been realized so far. Herein, greatly improved PL QYs of Mn 2+ emissions are reported in Mn 2+doped CsPbCl 3 NCs with various Mn 2+ doping concentrations after CdCl 2 post-treatment at room temperature. Specifically, the near-unity QY and near single-exponential decay of red Mn 2+ emission peaking at 627 nm in doped CsPbCl 3 NCs are obtained for the first time. The temperature dependence of steady-state and time-resolved PL spectra reveals that the CdCl 2 posttreatment significantly reduces the nonradiative defect states and enhances the energy transfer from host to Mn 2+ ions. Moreover, the Mn 2+ :CsPbCl 3 NCs after CdCl 2 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.

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The Mn2+-doped CsPbCl3 nanocrystals (NCs) with a low Mn2+ doping concentration were synthesized using different reaction temperatures to control the NC size from 5.3 to 17.4 nm and then were studied by means of steady-state and time-resolved photoluminescence (PL) spectroscopy at various temperatures. The Mn2+ emissions with different quantum yields in the doped NCs in hexane exhibited nearly size-independent and single-exponential decay lifetimes of 1.8 ms at room temperature. The PL lifetimes in all Mn2+ in CsPbCl3-doped NCs had similar temperature dependence from 80 to 300 K, whereas they were size-dependent at elevated temperatures, reflecting thermal degradation of doped NCs. The degradation mechanisms of Mn2+ PL were attributed to the amount of surface defects as nonradiative recombination centers generated in size-unchanged and grown Mn2+:CsPbCl3 NCs. The study provides the detailed understanding of the thermal degradation mechanisms in doped perovskite NCs for optoelectronic applications.