Photoluminescence Temperature Dependence, Dynamics, and Quantum Efficiencies in Mn2+-Doped CsPbCI3 Perovskite Nanocrystals with Varied Dopant Concentration

A series of Mn2+-doped CsPbCl3 nanocrystals (NCs) was synthesized using reaction temperature and precursor concentration to tune Mn2+ concentrations up to 14%, and then studied using variable-temperature photoluminescence (PL) spectroscopy. All doped NCs show Mn2+ T-4(1g) -> (6)A(1g) d-d luminescence within the optical gap coexisting with excitonic luminescence at the NC absorption edge. Room-temperature Mn2+ PL quantum yields increase with increased doping, reaching similar to 60% at similar to 3 +/- 1% Mn2+ before decreasing at higher concentrations. The low-doping regime is characterized by single exponential PL decay with a concentration-independent lifetime of 1.8 ms, reflecting efficient luminescence of isolated Mn2+. At elevated doping, the decay is shorter, multiexponential; and concentration-dependent, reflecting the introduction of Mn2+ Mn2+ dimers and energy migration to traps. A large, anomalous decrease in Mn2+ PL intensity is observed with decreasing temperature, stemming from the strongly temperature-dependent exciton lifetime and slow exciton-to-Mn2+ energy transfer, which combine to give a strongly temperature-dependent branching ratio for Mn2+ sensitization.