Complete Dopant Substitution by Spinodal Decomposition in Mn-Doped Two-Dimensional CsPbCl₃ Nanoplatelets

Abstract

The introduction of dopants plays a key role in the physical properties of semiconductors for optoelectronic applications. However, doping is generally challenging for nanocrystals (NCs), especially for two-dimensional (2D) NCs, due to the self-annealing effect and high surface energies required for dopant addition. Here, we report an efficient doping strategy for Mn-doped 2D CsPbCl3 (i.e., Mn:CsPbCl3) nanoplatelets (NPLs) through a postsynthetic solvothermal process. While the original lightly doped 2D Mn:CsPbCl3 NPLs were obtained from growth doping, higher Mn doping efficiencies were achieved through diffusion doping under pressure-mediated solvothermal conditions, resulting in enhanced Mn photoluminescence (PL). Surprisingly, a new CsMnCl3 phase with complete dopant substitution by spinodal decomposition was observed with extended solvothermal treatment, which is confirmed by powder X-ray diffraction, X-ray absorption fine structure, and electron paramagnetic resonance. Compared with Mn:CsPbCl3 NPLs, the pure CsMnCl3 NPLs give rise to shorter Mn PL lifetime, which is consistent with the short Mn–Mn distance within CsMnCl3 NPLs. This work provides an efficient strategy for doping inside NCs as well as new insights on the dopant concentration-dependent structural and optical properties of perovskite NCs.

Lead‐Free Semiconductors: Soft Chemistry, Dimensionality Control, and Manganese‐Doping of Germanium Halide Perovskites

“…I.). The small XRD peak shifts are consistent with reports of Mn 2+ doping into CsPbX 3 even at high doping levels ,,. The shift to lower 2θ angles is consistent with lattice expansion due to 6‐coordinate replacement of Ge 2+ ion (87 pm) with the larger high‐spin Mn 2+ ion (97 pm, see below) .…”

“…Interestingly, a similar observation is observed for Mn 2+ ‐doped CsPbCl 3 at low temperatures that induce phase transitions to lower symmetry structures . The hyperfine splitting constants of 90–96 G are larger than the 86–87 G values recently observed for Mn 2+ ‐doped CsPbCl 3 ,,,,,,,which is consistent with the higher lattice ionicity of germanium halide perovskites…”

“…[80] Interestingly, a similar observation is observed for Mn 2 + -doped CsPbCl 3 at low temperatures that induce phase transitions to lower symmetry structures. [81] The hyperfine splitting constants of 90-96 G are larger than the 86-87 G values recently observed for Mn 2 + -doped CsPbCl 3 , [60,63,64,66,78,81,82] which is consistent with the higher lattice ionicity of germanium halide perovskites. [83] Considering Vegard's Law, [84,85] we estimate we can incorporate Mn 2 + ions up to 29% in bulk and up to 16% in nanocrystalline samples ( Figure 5).…”

Solvothermal synthesis of Mn-doped CsPbCl3 perovskite nanocrystals with tunable morphology and their size-dependent optical properties

“…The Mn 2+ luminescence lifetime curve can be better tted to two-exponential decays than single-exponential decay, indicating that the formation of new CsMnCl 3 phase causes heterogeneous environment around Mn 2+ ions. 56 We further studied the effects of solvothermal reaction times on the optical properties of Mn-doped CsPbCl 3 NPLs. PL emission spectra (Fig.…”

“…It is noteworthy that the as-prepared ultrathin Mn-doped CsPbCl 3 NPLs have a thickness of down to $2 nm, which, as far as we know, has not been achieved in other works. 55,56 The strategy provides a platform for further study on the mixing process of metal doping and crystal growth, which can be used as a reference for the property regulation of metal-doped perovskite NCs.…”