Ab Initio Site‐Selective Occupancy and Luminescence Enhancement in Broadband NIR Emitting Phosphor Mg₇Ga₂GeO₁₂:Cr³⁺

Abstract

Cr3+ activated near‐infrared (NIR) phosphors are getting unprecedented attention to fabricate the broad band NIR light emitting diodes (NIR‐LEDs) for nondestructive detection, bio‐imaging, and night vision. However, it remains a major challenge to obtain ultrabroadband NIR emitting phosphor with excellent quantum yield (QY). Here, a broadband NIR emitting phosphor Mg7Ga2GeO12:Cr3+ (MGGO: Cr3+) ranging from 600 to 1300 nm with an outstanding QY (93%) and large full width of half maximum (FWHM = 226 nm) is developed, in which the site occupancy tendency of Cr3+ in MGGO host is discussed in detail through combining the structure optimization and the first‐principles theory calculation with luminescent properties at low temperature. After that, the emission intensity of MGGO:Cr3+ is improved through partial substitution of Mg2+ by alkaline‐earth ions Ca2+, Sr2+, or Ba2+, and the luminescence enhancement mechanism is also investigated. Furthermore, the NIR pc‐LED device is fabricated by combining 450 nm blue LED chip with the brightest phosphor MGGO:Cr3+/Ba2+, and its potential applications are evaluated in the field of nondestructive detection, night vision, and bio‐imaging.

Near-infrared emission, energy transfer, and mechanisms of Mn2+ and Cr3+ Co-doped lead-free Cs2AgInCl6 double perovskites

“…Multisite occupation refers to provision of two or more octahedral cation sites for Cr 3+ ions within the matrix. This method has been confirmed to be effective in Li 1.6 Zn 1.6 Sn 2.8 O 8 :Cr 3+ (FWHM = 190 nm) 27,28 and La 2 MgZrO 6 (FWHM = 210 nm). 29 The typical impurity doping strategy was multidoping with Nd, Yb, Er and Tm; Cs 2 AgInCl 6 :Bi/Ln showed an ultra-broadband continuous emission spectrum with a FWHM of about 365 nm.…”

K2LiScF6:Cr3+/Mn4+fluoride phosphor with enhanced broadband emission for NIR pc-LEDs

“…Meanwhile, two broad excitation bands in the blue ( peak at 432 nm) and red ( peak at 635 nm) regions dominate the PLE spectrum, which correspond to 4 A 2 → 4 T 1 and 4 A 2 → 4 T 2 transitions of Cr 3+ , respectively. 23 Generally, the PL properties of Cr 3+ are highly dependent on the crystal field strength (CFS) when located in an octahedral site. 24 A broadband emission Paper Dalton Transactions can be observed in a weak CFS, whereas a sharp line emission will be expected in a strong CFS, as shown in the Tanabe-Sugano diagram (Fig.…”

Near-infrared luminescence and high thermal stability of Rb2NaScF6:Cr3+ phosphor for spectroscopy applications

“…11 Compared with oxide host, i.e. , Mg 7 Ga 2 GeO 12 or Li 2 MgZrO 4 , 12,13 the low phonon energy as well as the weak electron–phonon coupling (EPC) strength of fluoride enables its attraction to produce efficient Cr 3+ -doped NIR phosphor. To date, Cr 3+ -doped fluorides have attracted widespread attention.…”