Probing Local Structural Changes by Sharp Luminescent Infrared Nanophosphor for Application in Light-Emitting Diodes

Abstract

Cr3+-doped infrared phosphors are promising candidates for next-generation phosphor-converted infrared light-emitting diodes (LEDs) because they can, in principle, tune and convert the luminescence spectra from an LED chip. However, most studies focus on broad-band Cr3+-doped phosphors, and the control mechanism of Cr3+-doped phosphors with sharp line emissions remains ambiguous. Here, we report LiGa5(1–x)Al5x O8:Cr3+ phosphors with sharp line emissions. The luminescence analysis reveals the subtle change of the local structure around Cr3+, which cannot be well resolved by X-ray diffraction. The deviation between the temperature-dependent photoluminescence and decay profile is introduced as well. Furthermore, the morphologies of LiGa5(1–x)Al5x O8:Cr3+ phosphors with high aluminum concentration demonstrate their great potential for mini-LED applications. Finally, an LED package is constructed, and it reveals the potential for angiographic applications. This study opens up a new understanding and perspective for Cr3+-doped sharp emission phosphors and reveals their potential for LED applications.

Concentration‐Induced Hetero‐Valent Partial‐Inverse Occupation of Infrared Phosphor

“…In our earlier study, we also demonstrated that in LiAl 5 O 8 , as the homeotypic structure of LiGa 5 O 8 , part of the Li occupies the Al octahedral site, and part of the Al occupies the Li sites, proving the possibility of the partial‐inverse occupation. [ 6 ] Similar perspective is also provided by Khaidukov et al. in the LiAl 5 O 8 :Cr 3+ system.…”

“…In our earlier study, we also demonstrated that in LiAl 5 O 8 , as the homeotypic structure of LiGa 5 O 8 , part of the Li occupies the Al octahedral site, and part of the Al occupies the Li sites, proving the possibility of the partial-inverse occupation. [6] Similar perspective is also provided by Khaidukov et al in the LiAl 5 O 8 :Cr 3+ system. [5a] With the similar ionic radii between Ga 3+ and Cr 3+ , this partial-inverse occupation may also happen at high Cr concentrations, leading to an unexpected Cr2 emission (Figure 3b) and broadening of the Raman peaks (Figure S3, Supporting Information).…”

“…[ 5 ] In our previous study, we investigated its luminescent properties by tuning the crystallographic structure. [ 6 ] However, due to the complex crystal structure and the potential inverse occupation, the structural and luminescent properties still remain ambiguous.…”

Highly efficient and thermally stable broadband near-infrared emitting garnet Ca3Sc2Ge3O12:Cr3+,Ce3+ phosphors for multiple pc-LED applications

“…The calculated lattice distortion index D values of [CaO 8 ] exhibited an increase from 1.41 to 2.32% in Table S2b (ESI†). 38–41 This proves our inference that the doping of Ce 3+ distorts the [CaO 8 ] dodecahedron and improves the d–d forbidden transition, which leads to a continuous increase in the NIR emission intensity under 480 nm excitation. The IQE of CSGG:0.14Cr 3+ ,0.16Ce 3+ is measured to be 61% under 480 nm excitation, which is nearly 3 times higher than that of CSGG:0.14Cr 3+ without Ce 3+ (IQE = 22%).…”

Unraveling Luminescent Energy Transfer Pathways: Futuristic Approach of Miniature Shortwave Infrared Light-Emitting Diode Design

“…After pressure is used, the shrinkage of the crystal lattice decreases the distance between Cr 3+ ions forming the ion pair, and the strength of the interaction increases. The stronger interaction between Cr 3+ ions in a pair will result in a greater distance from the Cr 3+ –Cr 3+ luminescence to the R-line of isolated Cr 3+ . The applied pressure shifts Ni 2+ emission linearly toward higher energies at a rate of 100 ± 10 cm –1 /GPa ( x = 0.02 + H 3 BO 3 flux) and 104 ± 4 cm –1 /GPa ( x = 0.02) due to the pressure-induced increase of the crystal field strength.…”