Effective optical tuning via Mn ²⁺ -driven 3D-to-quasi-2D ( n = 2) phase transition in CsPbBr

MnBr ₂ post-processing achieves 3D-to-quasi-2D phase transition. The Mn ²⁺ -doped OAm ₂ CsPb ₂ Br ₇ microcrystals emit at 616 nm with 45% PLQY. High Mn concentration builds chemical potential gradients to trigger spontaneous Mn ²⁺ /Pb ²⁺ ion exchange.