Exciton Recombination versus Energy Transfer: Mapping Competing Excited-State Dynamics in Various Mn-Doped CsPb(Cl1–yBry)3 Perovskite Nanocrystals for Achieving White Light Emission

Mn-doped lead halide perovskite nanocrystals provide considerable opportunities to improve the photoluminescence quantum yield and stability and to modulate the optoelectronic and magnetic properties of the nanocrystals through doping. However, excited-state charge carrier recombination within host lattices and competing exciton-to-dopant energy transfer indeed require a deeper understanding of the complicated excited-state dynamics. Here, we have thus investigated such competing exciton recombination versus energy transfer dynamics seen in Mn-doped CsPb(Cl1–yBry)3 nanocrystals as a function of precisely controlling the Mn concentration and Br/Cl composition. The concentration of the dopant across the host lattice of the nanocrystals and the halide composition with a tunable band gap indeed determine the rate of forward (exciton-to-Mn) and backward energy transfer (Mn-to-exciton). Two different Mn concentration regimes (lightly vs heavily doped) are found with different excited-state behaviors while modulating the halide composition. Understanding such competing radiative, nonradiative, and forward and backward energy transfers observed in Mn states that are strongly dependent on the concentration of Mn and the band gap of the host nanocrystals (halide composition) can provide significant insights into full utilization of the dual-emissive features in the transition metal-doped lead halide perovskite nanocrystals.