Review—Photoluminescence Properties of Cr³⁺-Activated Oxide Phosphors

Abstract

The Cr3+-activated phosphor properties are discussed in detail from an aspect of spectroscopic point of view. The host materials considered here are a various kind of oxide compounds. The photoluminescence (PL) and PL excitation spectra of the Cr3+-activated oxide phosphors are analyzed based on Franck−Condon analysis within the configurational-coordinate model. A new method is proposed for obtaining reliable crystal-field (Dq) and Racah parameters (B and C) based on a general ligand field theory with paying an attention to difficulty in the exact estimation of such important ligand field parameters. The intra-d-shell Cr3+ states, such as 2 E g (2 G), 4 T 2g (4 F), and 4 T 1g (4 F), in various oxide hosts are determined and plotted against Dq in the Tanabe−Sugano energy-level diagram. The results obtained are summarized in graphical and tabular forms. A comparative discussion of Cr3+ ion as an efficient activator in oxide and fluoride hosts is also given. The present analysis method can be used to predict an energy of Cr3+ emission and/or to check a validity of the Racah parameter values for a variety of Cr3+-activated phosphors and related optical and optoelectronic device applications.

A broadband near‐infrared Sc1−x(PO3)3:XCr3+ phosphor with enhanced thermal stability and quantum yield by Yb3+ codoping

“…Such a broadband NIR emission with the peak wavelength (λ em = 900 nm) is longer than other Cr 3+ -doped phosphates, indicating a weaker crystal field in Sc(PO 3 ) 3 . 16 The emission band of Sc 0.995 (PO 3 ) 3 :0.005Cr 3+ does not present a multicenter emission characteristic, even though there are three different crystallographic Sc 3+ sites in Sc(PO 3 ) 3 . For the Cr 3+ ion, it is in fact preferable to occupy the Sc 3+ site of Sc(1)O 6 octahedron.…”

“…10,11 Compared to the lanthanide ions (Nd 3+ , Yb 3+ , Er 3+ , Tm 3+ ), Cr 3+ ion can be served as a preferable NIR emitter, because it has a broadband absorption in the visible region (well matched with the blue-emitting chips), and an intense sharp-line emission (typically located around 690 nm) from the 2 E→ 4 A 2 transition in a strong crystal field, or a broadband emission from the 4 T 2g (4 F)→ 4 A 2 transition in a weak crystal field. [12][13][14][15][16][17][18] Thus, seeking for efficient Cr 3+ -doped broadband NIR phosphors has become a hot topic in the field of luminescent materials. [19][20][21][22][23][24][25][26][27] Until now a great progress has been made for the phosphors with emission peak wavelength less than 850 nm, which have a high internal and/or external quantum efficiency (IQE/EQE), superior thermal resistance quenching, and striking electro-optical efficiency.…”

“…Compared to the lanthanide ions (Nd 3+ , Yb 3+ , Er 3+ , Tm 3+ ), Cr 3+ ion can be served as a preferable NIR emitter, because it has a broadband absorption in the visible region (well matched with the blue‐emitting chips), and an intense sharp‐line emission (typically located around 690 nm) from the 2 E→ 4 A 2 transition in a strong crystal field, or a broadband emission from the 4 T 2g (4 F)→ 4 A 2 transition in a weak crystal field 12–18 . Thus, seeking for efficient Cr 3+ ‐doped broadband NIR phosphors has become a hot topic in the field of luminescent materials 19–27 .…”

Near-Infrared Phosphorescent Hybrid Organic–Inorganic Perovskite with High-Contrast Dielectric and Third-Order Nonlinear Optical Switching Functionalities

“… 4 In the case of metal centers, Cr 3+ is one of the most important PL species. 19 − 22 PL associated with this transition metal cation depends strongly on the crystal field strength and changes from a broad band in the near-IR (NIR) region for the weak crystal field ( 4 T 2g → 4 A 2g fluorescence) to narrow in the red region (usually near 700 nm) for the Cr 3+ in the strong crystal field ( 2 E g → 4 A 2g phosphorescence). 19 , 20 , 23 The phosphorescence of a ruby was utilized for construction of a solid-state red laser.…”

“… 19 − 22 PL associated with this transition metal cation depends strongly on the crystal field strength and changes from a broad band in the near-IR (NIR) region for the weak crystal field ( 4 T 2g → 4 A 2g fluorescence) to narrow in the red region (usually near 700 nm) for the Cr 3+ in the strong crystal field ( 2 E g → 4 A 2g phosphorescence). 19 , 20 , 23 The phosphorescence of a ruby was utilized for construction of a solid-state red laser. 24 Recently, there is growing interest in finding materials exhibiting efficient emission in the NIR region because such radiation has good penetration of organic matter and finds application in bioimaging, sensors, photovoltaics, optical communications, etc.…”