Thickness-Dependent Photoluminescence Properties of Mn-Doped CsPbBr3 Perovskite Nanoplatelets Synthesized at Room Temperature

Mn-doped CsPbBr3 perovskite nanoplatelets (NPLs) with multicolor emission have very promising applications in light-emitting devices. However, the effects of NPL thickness on the Mn2+ luminescence properties remain to be investigated. Herein, a series of Mn-doped CsPbBr3 NPLs and nanocubes with different Mn/Pb molar ratios were synthesized by a supersaturated crystallization method at room temperature. The incorporation of Mn2+ ions into CsPbBr3 perovskites is attributed to the formation of the L2[Pb1–xMnx]Br4 intermediate structure in the precursor. The excitonic peak is tuned from 437 to 488 nm and the morphology evolves from NPLs to nanocubes with an increasing Mn2+ ion doping concentration due to the excess Br– from MnBr2. The photoluminescence quantum yields (PL QYs) of NPLs/nanocubes were greatly enhanced, achieving the maximum PL QYs of 88.7% at the Mn/Pb molar ratio of 3/1. The PL lifetime of Mn2+ emission is tuned from 0.19 to 0.44 ms due to the passivation of defect states and morphology transformation. Temperature-dependent steady-state and time-resolved PL spectra revealed that deep defect states in the NPLs/nanocubes were significantly reduced as the thickness increased. The Mn-doped CsPbBr3 NPLs/nanocubes show great potential for application in white light-emitting diodes.