All-inorganic CsPbBr3 nanocrystals (NCs) are promising materials for next-generation optoelectronic devices owing to their high photoluminescence quantum yield, narrow emission linewidth, and excellent color purity. Although efficient green-emitting CsPbBr3 NCs have been widely demonstrated, the development of stable blue-emitting materials remains a major challenge [1]. Most reported approaches rely on mixed-halide CsPb(Br/Cl)3 nanocrystals, which often suffer from photoinduced halide migration and spectral instability. Therefore, alternative strategies based on controlling nanocrystal growth have attracted increasing attention.

In this work, we investigate the effect of Mn(CH₃COO)₂ on the crystallization of CsPbBr3 nanocrystals during ligand-assisted reprecipitation (LARP) synthesis. CsPbBr3 nanocrystals were synthesized using ethylbenzene, toluene, and ethyl acetate as antisolvents in the presence of Mn(CH₃COO)₂, employing CsPbBr3:Mn(CH₃COO)₂ precursor molar ratios of 1:0, 1:1.1, 1:3.4, and 1:10.0. The obtained nanocrystals were characterized by UV–Vis absorption spectroscopy, photoluminescence (PL) spectroscopy, and transmission electron microscopy (TEM).

The absorption spectra showed a pronounced dependence on both the CsPbBr3:Mn(CH₃COO)₂ precursor molar ratio and the nature of the antisolvent. The samples synthesized in ethyl acetate exhibited a single excitonic absorption band, whose absorption maximum gradually shifted from 506 to 470–472 nm as the Mn(CH₃COO)₂ proportion increased. In contrast, the nanocrystals synthesized in ethylbenzene and toluene developed additional short-wavelength absorption bands at CsPbBr3:Mn(CH₃COO)₂ precursor molar ratios of 1:3.4 and 1:10.0, indicating the presence of an additional population of nanocrystals with a wider band gap, most likely associated with smaller particle sizes.

The photoluminescence spectra were consistent with the absorption behavior. The Mn(CH₃COO)₂-free CsPbBr3 nanocrystals (precursor molar ratio of 1:0) exhibited a single green emission band centered at approximately 523 nm, regardless of the antisolvent. Increasing the Mn(CH₃COO)₂ proportion to a CsPbBr3:Mn(CH₃COO)₂ precursor molar ratio of 1:1.1 resulted in a hypsochromic shift of the emission maximum while preserving single-band emission. Further increasing the Mn(CH₃COO)₂ proportion (precursor molar ratios of 1:3.4 and 1:10.0) led to the appearance of additional blue emission bands for nanocrystals synthesized in ethylbenzene and toluene. At the same time, samples prepared in ethyl acetate retained a single emission band throughout the investigated precursor molar ratio range, accompanied only by a gradual blue shift.

TEM analysis revealed that the presence of Mn(CH₃COO)₂ during synthesis alters the nanocrystal growth pathway. In the absence of Mn(CH₃COO)₂ (precursor molar ratio of 1:0), the products consisted predominantly of relatively uniform square-shaped nanocrystals. In contrast, samples prepared with Mn(CH₃COO)₂ exhibited a significantly broader distribution of particle sizes and morphologies, including elongated anisotropic nanocrystals and a distinct population of smaller nanocrystals. These morphological observations are consistent with the spectroscopic results and suggest that Mn²⁺ modifies crystal growth and likely influences the nucleation process. This interpretation is further supported by the spectroscopic evidence of enhanced quantum confinement within a fraction of the nanocrystal population.

Importantly, none of the investigated samples exhibited the characteristic Mn²⁺ orange emission (~600 nm). Therefore, the observed evolution of the photoluminescence is attributed mainly to Mn²⁺-induced changes in the crystallization process and nanocrystal morphology, rather than to direct Mn²⁺ doping. These results indicate that Mn²⁺ primarily acts as a crystallization modifier, regulating crystal growth rather than contributing to Mn²⁺-related photoluminescence. The additional short-wavelength optical features are attributed to a population of smaller and/or more anisotropic nanocrystals exhibiting stronger quantum confinement.

This approach opens new opportunities for developing spectrally stable blue-emitting perovskite nanomaterials for future optoelectronic applications.