Manganese (Mn)-based organic–inorganic metal halides (OIMHs) are extensively employed in various optical applications due to their non-toxicity, superior optical properties, and tunable emission advantages. Developing effective strategies to enhance the optical properties of these materials and clarifying their structure–optical property relationships continue to be of significant interest. Here, we report that the zero-dimensional (0D) (C24H20P)2MnBr4 exhibits remarkable pressure emission tuning that shifts from green to red, a phenomenon driven by the enhancement of the crystal field splitting energy and the reduced energy difference of the lowest d–d transition (4T1 → 6A1) motivated by the shortening of Mn–Br bonds. Additionally, the band gap value of (C24H20P)2MnBr4 becomes 3.13 eV, showing an unexpected decrease by 1.09 eV from an initial value of 4.22 eV, when the pressure is released from 31.0 GPa. The incomplete recovery of the distortion in [MnBr4]2− tetrahedra, impeded by the distortion of soft organic macromolecules, is believed to be responsible for band gap narrowing. Combined with computations and subsequent experiments, it is inferred that pressure induced reduction in the Mn–Br bond distance contributes to the distortion of tetrahedral [MnBr4]2− and larger-sized organic cations. Our work not only elucidates the structure–optical property relationships in Mn-based OIMHs, but also opens new avenues for modulating their optical properties and devising innovative strategies for designing novel Mn-based OIMHs.
Fe 3+ ions as near-infrared (NIR) activators are emerging as an alternative to Cr 3+ . 1–5 However, it is a challenge to develop Fe 3+ -activated NIR phosphors featuring tunable optical properties, high efficiency, and thermal stability. Herein, we present a series of near-unity internal quantum efficiency (IQE), wavelength-tunable and thermal stability NIR-emitting phosphors Sr 2− y Ca y Sc 1− x SbO 6 : x Fe 3+ (S 2− y C y S 1− x S: x Fe 3+ ). Sr 2 ScSbO 6 :1%Fe 3+ (SSS:1%Fe 3+ ) phosphor shows broadband NIR emission at 904 nm and near-unity IQE under excitation at 300 nm. Experimental and theoretical calculation results demonstrate that introduced Ca ions could increase the bandgap value and Debye temperature (Θ D ) of host from E g = 3.702 eV, Θ D = 609 K of y = 0 to E g = 3.801 eV, Θ D = 692 K of y = 2. Significantly, the resultant S 2− y C y S 1− x S:1%Fe 3+ NIR phosphors show wavelength-tunable emission from 904 to 952 nm and high IQE of 84.6%–97.5% as well as enhanced thermal stability ( I 423K / I 298K = 76.9%) of Ca 2 ScSbO 6 :1%Fe 3+ (CSS:1%Fe 3+ ) in comparison with that ( I 423K / I 298K = 70.6%) of pristine sample. We fabricated an NIR light-emitting diodes (LED) device by using CSS:1%Fe 3+ NIR phosphors with ultraviolet LED chip and demonstrated its potential applications in anticounterfeiting, information encryption, and night vision.
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