Crystal‐Field Engineering Control of an Ultraviolet–Visible‐Responsive Near‐Infrared‐Emitting Phosphor and Its Applications in Plant Growth, Night Vision, and NIR Spectroscopy Detection

Abstract

Broadband near‐infrared (NIR) phosphor‐converted light‐emitting diodes (pc‐LEDs) have many prospective applications in areas related to food inspection, health management, plant growth, and night vision, because NIR phosphors are critical components of the corresponding devices. Given the wide‐ranging applicability of the material, this study is designed to comprehensively evaluate a series of novel NIR phosphors: BaMgGaxAl10–xO17:Cr3+ (x = 0, 1, 2, 3). The ultra‐low‐temperature (4 K) fluorescence spectroscopy and decay curve results confirm that Cr3+ occupies the four lattice sites of Al3+ in the matrix. Additionally, the introduction of Ga3+ increases the full‐width at half‐maximum (FWHM) of the NIR spectrum from 100 to 300 nm without affecting the fluorescence efficiency; it also considerably increases spectral coverage. An experiment to evaluate the applicability of the novel NIR phosphors reveals that the sunlight‐converting film prepared by applying the material combination of BaMgGa3Al7O17:0.02Cr3+ is able to effectively promote the growth of Chlorella. In addition, the NIR pc‐LED with a BaMgGa3Al7O17:0.2Cr3+ basis and 395‐nm LED chip has been proven to be an excellent candidate for applications in NIR spectral detection and night‐vision technology.

Interstitial Li+ Occupancy Enabling Radiative/Nonradiative Transition Control toward Highly Efficient Cr3+-Based Near-Infrared Luminescence

“…As mentioned above, the emission of Cr 3+ originates from the parity-forbidden d–d transition; thus, it is necessary to introduce a distorted crystal-field environment to break the selection rule limitation to increase the luminescence efficiency. To date, several effective approaches including site engineering, chemical unit cosubstitution, and single-cation substitution have been developed. Because of the decreased local environment symmetry for Cr 3+ , the NIR efficiency of the related phosphors was improved to some degree.…”

Enhancing the luminescence performance of Ca2−xSrxBO3Cl:Eu2+,Dy3+ by substitution of Sr2+ for Ca2+

“…In recent years, the design and modulation of phosphors by replacing anions or ionic groups with solid solution have become one of the research hotspots. Denalt et al found that the luminescence performance of Ba 2− x Sr x SiO4:Eu 2+ samples could be substantially improved by using the substitution of the same main group ion Sr 2+ in Ba 2 SiO 4 :Eu 2+ , which is because Sr 2+ substitution increased the thermal stability of phosphors and produced a more rigid crystal structure; 20 Xia pointed out that the the fluorescence performance of Ca 2 (Al 1− x Mg x )(Al 1− x Si 1+ x )O 7 :Eu 2+ could see significant improvements by replacing the [Al 3+ –Al 3+ ] structural unit with [Mg 2+ –Si 4+ ] to facilitate the electron–phonon coupling effect; 21 Lin et al substituted CaYAlO 4 :Eu 2+ ,Eu 3+ phosphors with [Si 4+ –Al 3+ ], [Ca 2+ –Y 3+ ] to make the octahedral lattice of AlO 6 shrink and the polyhedral lattice of CaO 9 expand, so that some of the Eu 3+ ions are reduced to Eu 2+ and the luminous color of the samples is adjustable; 22 Zhou noted that the near-infrared spectrum coverage of BaMgGa x Al 10− x O 17 :Cr 3+ was greatly enhanced through the solid solution with Ga 3+ and Al 3+ and the half-peak width increased from 100 nm to 300 nm, and the substitution of Ga 3+ for Al 3+ led to an increase in CrO bond stress, a decrease in the bond length and an increase in energy level cleavage, resulting in a significant improvement in the optical properties of the sample; 23 Ma et al investigated a 2000% increase in initial afterglow luminance and 350% increase in afterglow time in the BaGa 2− x Zn x O 4 :Pr 3+ series of samples; 24 Xie found that the trap depth of Y 3 Al 5− x Ga x O 12 :Ce 3+ ,V 3+ ( x = 0–3) could be adjusted by solid solution of Al 3+ by Ga 3+ , resulting in the change of the crystal field intensity. Meanwhile, the solid solution of Ga 3+ led to the adjustment of the luminescence color of the sample from green to yellow, which has a good application prospect for optical storage.…”

Luminescence properties and energy transfer of the near-infrared phosphor Ca3In2Ge3O12:Cr3+,Nd3+

“…9b, the thermal quenching activation energy of CIG:0.07Cr 3+ ,0.15Nd 3+ was further calculated using the Arrhenius equation (eqn (6)). 33,34 …”