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Charge deformation and orbital hybridization: intrinsic mechanisms on tunable chromaticity of Y3Al5O12:Ce3+ luminescence by doping Gd3+ for warm white LEDs.

Chen L, Chen X, Liu F, Chen H, Wang H, Zhao E, Jiang Y, Chan TS, Wang CH, Zhang W, Wang Y, Chen S - Sci Rep (2015)

Bottom Line: The deficiency of Y3Al5O12:Ce (YAG:Ce) luminescence in red component can be compensated by doping Gd(3+), thus lead to it being widely used for packaging warm white light-emitting diode devices.A new interpretation from the viewpoint of compression deformation of electron cloud in a rigid structure by combining orbital hybridization with solid-state energy band theory together is put forward to illustrate the intrinsic mechanisms that cause the emission spectral shift, thermal quenching, and luminescence intensity decrease of YAG: Ce upon substitution of Y(3+) by Gd(3+), which are out of the explanation of the classic configuration coordinate model.The results indicate that in a rigid structure, the charge deformation provides an efficient way to tune chromaticity, but the band gaps and crystal defects must be controlled by comprehensively accounting for luminescence thermal stability and efficiency.

View Article: PubMed Central - PubMed

Affiliation: School of Materials Science and Engineering, Hefei University of Technology, Hefei 230009, China.

ABSTRACT
The deficiency of Y3Al5O12:Ce (YAG:Ce) luminescence in red component can be compensated by doping Gd(3+), thus lead to it being widely used for packaging warm white light-emitting diode devices. This article presents a systematic study on the photoluminescence properties, crystal structures and electronic band structures of (Y1-xGdx)3Al5O12: Ce(3+) using powerful experimental techniques of thermally stimulated luminescence, X-ray diffraction, X-ray absorption near edge structure (XANES), extended X-ray absorption fine structure (EXAFS) and ultraviolet photoelectron spectra (UPS) of the valence band, assisted with theoretical calculations on the band structure, density of states (DOS), and charge deformation density (CDD). A new interpretation from the viewpoint of compression deformation of electron cloud in a rigid structure by combining orbital hybridization with solid-state energy band theory together is put forward to illustrate the intrinsic mechanisms that cause the emission spectral shift, thermal quenching, and luminescence intensity decrease of YAG: Ce upon substitution of Y(3+) by Gd(3+), which are out of the explanation of the classic configuration coordinate model. The results indicate that in a rigid structure, the charge deformation provides an efficient way to tune chromaticity, but the band gaps and crystal defects must be controlled by comprehensively accounting for luminescence thermal stability and efficiency.

No MeSH data available.


Related in: MedlinePlus

The emission and excitation spectra of (Y1−xGdx)2.94Al5O12: 0.06Ce3+ with normalized intensity(a) and the amplified region showing the crossover of the emission and excitation upon different amount of Gd3+.
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f7: The emission and excitation spectra of (Y1−xGdx)2.94Al5O12: 0.06Ce3+ with normalized intensity(a) and the amplified region showing the crossover of the emission and excitation upon different amount of Gd3+.

Mentions: Moreover, there are two facts that cannot be explained with the traditional configuration coordinate diagram. First, the soft structure indicates a large Stokes’ shift. Accordingly, the nonradiative energy loss with electrons relaxed from the 5d excited state to the 4f ground state through the crossover of their potential parabolas should increase with increasing Gd3+. However, the overlap of the normalized excitation and emission spectra of (Y1−xGdx)3Al5O12: Ce3+ decreases with an increase of Gd3+ content in x value (as seen below in Fig. 7), indicating that the nonradiative transition does not increase. Second, the thermal vibration of the crystal lattice strongly depends on the weight of the atoms, and a heavy weight is helpful resisting thermal vibration. To this end, the thermal stability of YAG: Ce should be improved after doping with Gd3+ because of its heavier weight compared with Y3+. Practically, this result is not observed. Hence, some mechanisms should exist that play a more important role than the thermal vibration of the crystal lattice and are beyond the range of what the configuration coordinate theory can explain.


Charge deformation and orbital hybridization: intrinsic mechanisms on tunable chromaticity of Y3Al5O12:Ce3+ luminescence by doping Gd3+ for warm white LEDs.

Chen L, Chen X, Liu F, Chen H, Wang H, Zhao E, Jiang Y, Chan TS, Wang CH, Zhang W, Wang Y, Chen S - Sci Rep (2015)

The emission and excitation spectra of (Y1−xGdx)2.94Al5O12: 0.06Ce3+ with normalized intensity(a) and the amplified region showing the crossover of the emission and excitation upon different amount of Gd3+.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4502399&req=5

f7: The emission and excitation spectra of (Y1−xGdx)2.94Al5O12: 0.06Ce3+ with normalized intensity(a) and the amplified region showing the crossover of the emission and excitation upon different amount of Gd3+.
Mentions: Moreover, there are two facts that cannot be explained with the traditional configuration coordinate diagram. First, the soft structure indicates a large Stokes’ shift. Accordingly, the nonradiative energy loss with electrons relaxed from the 5d excited state to the 4f ground state through the crossover of their potential parabolas should increase with increasing Gd3+. However, the overlap of the normalized excitation and emission spectra of (Y1−xGdx)3Al5O12: Ce3+ decreases with an increase of Gd3+ content in x value (as seen below in Fig. 7), indicating that the nonradiative transition does not increase. Second, the thermal vibration of the crystal lattice strongly depends on the weight of the atoms, and a heavy weight is helpful resisting thermal vibration. To this end, the thermal stability of YAG: Ce should be improved after doping with Gd3+ because of its heavier weight compared with Y3+. Practically, this result is not observed. Hence, some mechanisms should exist that play a more important role than the thermal vibration of the crystal lattice and are beyond the range of what the configuration coordinate theory can explain.

Bottom Line: The deficiency of Y3Al5O12:Ce (YAG:Ce) luminescence in red component can be compensated by doping Gd(3+), thus lead to it being widely used for packaging warm white light-emitting diode devices.A new interpretation from the viewpoint of compression deformation of electron cloud in a rigid structure by combining orbital hybridization with solid-state energy band theory together is put forward to illustrate the intrinsic mechanisms that cause the emission spectral shift, thermal quenching, and luminescence intensity decrease of YAG: Ce upon substitution of Y(3+) by Gd(3+), which are out of the explanation of the classic configuration coordinate model.The results indicate that in a rigid structure, the charge deformation provides an efficient way to tune chromaticity, but the band gaps and crystal defects must be controlled by comprehensively accounting for luminescence thermal stability and efficiency.

View Article: PubMed Central - PubMed

Affiliation: School of Materials Science and Engineering, Hefei University of Technology, Hefei 230009, China.

ABSTRACT
The deficiency of Y3Al5O12:Ce (YAG:Ce) luminescence in red component can be compensated by doping Gd(3+), thus lead to it being widely used for packaging warm white light-emitting diode devices. This article presents a systematic study on the photoluminescence properties, crystal structures and electronic band structures of (Y1-xGdx)3Al5O12: Ce(3+) using powerful experimental techniques of thermally stimulated luminescence, X-ray diffraction, X-ray absorption near edge structure (XANES), extended X-ray absorption fine structure (EXAFS) and ultraviolet photoelectron spectra (UPS) of the valence band, assisted with theoretical calculations on the band structure, density of states (DOS), and charge deformation density (CDD). A new interpretation from the viewpoint of compression deformation of electron cloud in a rigid structure by combining orbital hybridization with solid-state energy band theory together is put forward to illustrate the intrinsic mechanisms that cause the emission spectral shift, thermal quenching, and luminescence intensity decrease of YAG: Ce upon substitution of Y(3+) by Gd(3+), which are out of the explanation of the classic configuration coordinate model. The results indicate that in a rigid structure, the charge deformation provides an efficient way to tune chromaticity, but the band gaps and crystal defects must be controlled by comprehensively accounting for luminescence thermal stability and efficiency.

No MeSH data available.


Related in: MedlinePlus