Green Synthesis of Dual-Emission Tin-Doped Cesium Manganese Halide Nanocrystals with High Performance

Manganese-based halide perovskites have gradually become a focus point for exploring photoluminescent materials due to their attractive electronic and photophysical properties. However, little attention has been paid to the dual-emission and thermochromic phenomena in all-inorganic Mn-based materials. In this study, Sn²⁺-doped Cs₃MnBr₃Cl₂ is synthesized at room temperature, which exhibits bright yellow emission, with two broad emission peaks at 525 and 605 nm, corresponding to full width at half-maximum (fwhm) of 92 and 91 nm, respectively. The photoluminescence quantum yield (PLQY) is significantly increased from 5.3% for the absence of Sn²⁺ to 33.41% for the presence of Sn²⁺. The excitation, temperature-dependent, and time-resolved spectra indicate that the dual emissions originate from the spin-forbidden transition (⁴T₁ → ⁶A₁) of Mn²⁺ and the self-trapped exciton emission induced by Sn²⁺ doping. The introduction of Sn²⁺ modifies the crystal field environment and symmetry around Mn²⁺, intensifying the electron-phonon coupling, thereby causing the emergence of a new emission peak and significant broadening of the fwhm. Furthermore, due to the different temperature sensitivities of the two emission peaks, the emitted color is transitioned from yellow to orange-red as the temperature is increased. Combined with its enhanced stability, this material demonstrates promising application potential in the optoelectronic field.