Origin and tunability of dual color emission in highly stable Mn doped CsPbCl₃ nanocrystals grown by a solid-state...

Herein, we report on a facile, bulk scale room temperature solid-state synthesis of highly stable and luminescent Mn-doped CsPbCl₃ nanocrystal (NCs) with high Mn substitution, and investigate the origin and tunability of its dual-color emission. The structural and compositional analyses confirm the successful doping of Mn (1-40%) ion in CsPbCl₃ NCs. The Mn-doped CsPbCl₃ NCs exhibit distinct excitonic photoluminescence (PL) emission at ~412 nm (I_ex) and Mn related emission at ~590 nm (I_Mn) with high PL quantum yield (up to 35%). Our study reveals that the intensity ratio I_Mn/I_ex could be widely tuned by a factor of 64 and 23 by changing the Mn concentration and the measurement temperature, respectively. The stronger Mn emission at higher temperature is attributed to the higher rate of transfer of photoexcited carriers from the excitonic state of CsPbCl₃ host to Mn related state. Further, excitation intensity-dependent PL along with time-resolved PL studies revealed important insights into the origin and tunability of Mn related orange-red PL in the dual color emitting Mn-doped CsPbCl₃ NCs. The PL line shape analysis revealed additional PL peak in the range ~634-666 nm, which grows stronger with higher doping concentration and it is attributed, for the first time, to structural defects in the NCs. Remarkably, the Mn-doped CsPbCl₃ NCs synthesized by our method exhibit about 10 times higher storage stability than those reported earlier due to the high Mn doping efficiencies achieved due to the strain induced enhanced doping process. Finally, white light emitting diodes (LEDs) were fabricated by employing blue-emitting CsPbCl_1.5Br_1.5 NCs, green-emitting CsPbBr₃ NCs and orange-red emitting 10% Mn-doped CsPbCl₃ NCs all grown by the same method. Our work demonstrates a low-cost synthesis strategy for high Mn doping in CsPbCl₃ NCs with superior ambient stability and highly tunable emission.