Uncovering the presence or absence of photoluminescence from iron ions in crystals

The poor understanding of the optical transitions and luminescent mechanisms critically hindered the development of near-infrared (NIR) ${\mathrm{Fe}}^{3+}$-activated phosphors, and efficient luminescence from Fe(Oh) has rarely been reported. In our study, we delve into these challenges and realize their correlation with the quenching mechanism of ${\mathrm{Fe}}^{3+}$ luminescence. First-principles calculations are utilized to analyze energy levels and electron-phonon coupling parameters, further elucidating potential deactivation pathways and factors influencing the occurrence of photoluminescence. A heuristic rule based on ligand-field strength, determined by the absorption wavelength of ${\mathrm{Cr}}^{3+}$ occupying the same octahedral site in oxides, is proposed to facilitate the prediction of both the potential and wavelength of ${\mathrm{Fe}}^{3+}$ emission. Our study offers consistent and reliable interpretations for the difficulties and challenges of iron-doped crystals, and provides valuable insights on the design and optimization of ${\mathrm{Fe}}^{3+}$-based phosphors.