Novel broadband near-infrared emitting long afterglow phosphor MgGeO3: Cr3+

Broadening of the near-infrared emission band of the Mg2Al4Si5O18:Cr3+ phosphor for illumination emission applications

“…The crystal field strength Dq and the Racah parameter B can be calculated using the following equations: 12,47,48 E ( 4 T 2 ) = 10 Dq where E ( 4 T 2 ) is the relative energy between 4 T 2 and 4 A 2 , and Δ E is the relative energy between 4 T 2 and 4 T 1 , which is determined according to the excitation or absorption spectra. The crystal field strength Dq of Cr1 was calculated to be 1754.0 cm −1 with a Dq / B value of 2.45, while that of Cr2 was 1582.0 cm −1 with a Dq / B value of 2.33.…”

“…The crystal field strength Dq and the Racah parameter B can be calculated using the following equations: 12,47,48 E( 4 T 2 ) = 10Dq…”

“…[8][9][10][11] Especially, Cr 3+ ions are well known for their broadband emission in NIR originating from the 4 T 2 -4 A 2 transition in an intermediate or a weak field. [12][13][14] So far, a number of Cr 3+ doped NIR phosphors with broadband emission have been reported such as Cs 2 KGaF 6 :Cr 3+ (l em = 782 nm, FWHM = 110 nm), 15 ZnWO 4 :Cr 3+ (l em = 980 nm, FWHM = 100 nm), 16 Ca 3 Sc 2 Si 3 O 12 :Cr 3+ (l em = 783 nm, FWHM = 92 nm), 17 CaSc 2 O 4 :Cr (l em = 819 nm, FWHM = 170 nm), 18 Y 3 Sc 2 Ga 3 O 12 :Cr 3+ (l em = 740 nm, FWHM = 90 nm), 19 ScBO 3 :Cr 3+ (l em = 800 nm, FWHM = 120 nm), 20 Gd 3 Ga 5 O 12 :Cr 3+ (l em = 717 nm, FWHM = 90 nm), 21 GdAl 3 (BO 3 ) 4 :Cr 3+ (l em = 740 nm, FWHM = 140 nm), 22 YAl 3 (BO 3 ) 4 :Cr 3+ (l em = 720 nm, FWHM = 100 nm), 23 NaIn(WO 4 ) 2 :Cr 3+ (l em = 1100 nm, FWHM = 115 nm), 24 LiSc(Si 1Àx Ge x ) 2 O 6 :Cr 3+ (l em = 900 nm, FWHM = 180 nm), 25 MgTa 2 O 6 :Cr 3+ (l em = 834 nm, FWHM = 140 nm), 26 NaAl(WO 4 ) 2 :Cr 3+ (l em = 815 nm, FWHM = 200 nm), 27 CaScAl-SiO 6 :Cr 3+ (l em = 950 nm, FWHM = 205 nm), 28 LiIn 2 SbO 6 (l em = 970 nm, FWHM = 225 nm), 29 Ca 2 LuGa 3 Ge 2 O 12 :Cr 3+ (l em = 803 nm, FWHM = 267 nm), 30 and so on. However, most of the Cr 3+ -doped NIR phosphors have a full width at half maximum (FWHM) of emission spectra of less than 200 nm.…”

Research progress of perovskite long afterglow materials

“…In addition, clear, bright luminous images representing recorded information became visible in the dark after heating the sample to a temperature of 200 1C, enabling unique writing (via red laser) and reading (via thermal stimulation) patterns, which offers prospects for information security applications. Guna Doke et al 74 successfully synthesized and studied for the first time novel wideband near-infrared emitting afterglow fluorophores with different Cr 3+ doping concentrations, i.e., MgGeO 3 . When excited by 263 nm ultraviolet radiation, all the samples demonstrated broad-spectrum emission in the NIR spectral region, spanning approximately 700-1200 nm.…”

“…72 (b) A schematic diagram of the PersL mechanism in the MGO:Cr 3+ material. 74 as electron traps. The mechanism of afterglow was be explained by the fact that under ultraviolet irradiation, electrons are excited directly to CB, leaving holes in the VB.…”