Mechanism of light emission and electronic properties of a Eu 3+-doped Bi2SrTa2O9 system determined by coupled X-ray absorption and emission spectroscopy

Ting Shan Chan, Chung Li Dong, Yi Hauan Chen, Ying Rui Lu, Sheng Yun Wu, Yuan Ron Ma, Chun Che Lin, Ru Shi Liu, Jeng Lung Chen, Jinghua Guo, Jyh Fu Lee, Hwo Shuenn Sheu, Chun Chuen Yang, Chi Liang Chen

Research output: Contribution to journalArticle

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Abstract

The origin of light emission from newly discovered orange-red UV light emitting diodes, and their electronic properties are critical issues yet to be understood. In this study, X-ray absorption spectroscopy (XAS) and emission spectroscopy (XES) are utilized to examine the electronic structure of the Eu3+-doped Bi2SrTa2O9 system. While no significant change in the electronic structure is observed around the Bi and Ta sites, variation around the Eu and Sr atoms is observed, along with even more significant changes in the O 2p states in the conduction band. Upon UV irradiation, Eu-induced states within the conduction band are observed and found to shift to the conduction band minimum upon substitution of Sr with Eu. This phenomenon is the result of the creation by Eu of an excitable state and the fact that Eu is more electronegative than Sr, such that the substitution lowers the Eu 4f5d-O 2p hybridized states. Consequently, the substitution reduces the energy of electron recombination between the valence and conduction bands, which is consistent with the red shift in the photoluminescence spectra. The presence of the newly formed hole states distributed over the O 2p states in the conduction band is strongly correlated with the emission intensity. The results and analyses demonstrate that Eu can be introduced to tailor the Eu-O hybridized states within the conduction band and change the route of recombination, suggesting that Eu is critically involved in light emission in these UV-induced orange-red emitting LED materials.

Original languageEnglish
Pages (from-to)17119-17127
Number of pages9
JournalJournal of Materials Chemistry
Volume21
Issue number43
DOIs
Publication statusPublished - Nov 21 2011
Externally publishedYes

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X ray absorption spectroscopy
Light emission
Conduction bands
Electronic properties
Substitution reactions
Electronic structure
Emission spectroscopy
Valence bands
Ultraviolet radiation
Light emitting diodes
X-Ray Emission Spectrometry
Photoluminescence
Diodes
Irradiation
Atoms
Electrons

ASJC Scopus subject areas

  • Chemistry(all)
  • Materials Chemistry

Cite this

Mechanism of light emission and electronic properties of a Eu 3+-doped Bi2SrTa2O9 system determined by coupled X-ray absorption and emission spectroscopy. / Chan, Ting Shan; Dong, Chung Li; Chen, Yi Hauan; Lu, Ying Rui; Wu, Sheng Yun; Ma, Yuan Ron; Lin, Chun Che; Liu, Ru Shi; Chen, Jeng Lung; Guo, Jinghua; Lee, Jyh Fu; Sheu, Hwo Shuenn; Yang, Chun Chuen; Chen, Chi Liang.

In: Journal of Materials Chemistry, Vol. 21, No. 43, 21.11.2011, p. 17119-17127.

Research output: Contribution to journalArticle

Chan, TS, Dong, CL, Chen, YH, Lu, YR, Wu, SY, Ma, YR, Lin, CC, Liu, RS, Chen, JL, Guo, J, Lee, JF, Sheu, HS, Yang, CC & Chen, CL 2011, 'Mechanism of light emission and electronic properties of a Eu 3+-doped Bi2SrTa2O9 system determined by coupled X-ray absorption and emission spectroscopy', Journal of Materials Chemistry, vol. 21, no. 43, pp. 17119-17127. https://doi.org/10.1039/c1jm11849h
Chan, Ting Shan ; Dong, Chung Li ; Chen, Yi Hauan ; Lu, Ying Rui ; Wu, Sheng Yun ; Ma, Yuan Ron ; Lin, Chun Che ; Liu, Ru Shi ; Chen, Jeng Lung ; Guo, Jinghua ; Lee, Jyh Fu ; Sheu, Hwo Shuenn ; Yang, Chun Chuen ; Chen, Chi Liang. / Mechanism of light emission and electronic properties of a Eu 3+-doped Bi2SrTa2O9 system determined by coupled X-ray absorption and emission spectroscopy. In: Journal of Materials Chemistry. 2011 ; Vol. 21, No. 43. pp. 17119-17127.
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abstract = "The origin of light emission from newly discovered orange-red UV light emitting diodes, and their electronic properties are critical issues yet to be understood. In this study, X-ray absorption spectroscopy (XAS) and emission spectroscopy (XES) are utilized to examine the electronic structure of the Eu3+-doped Bi2SrTa2O9 system. While no significant change in the electronic structure is observed around the Bi and Ta sites, variation around the Eu and Sr atoms is observed, along with even more significant changes in the O 2p states in the conduction band. Upon UV irradiation, Eu-induced states within the conduction band are observed and found to shift to the conduction band minimum upon substitution of Sr with Eu. This phenomenon is the result of the creation by Eu of an excitable state and the fact that Eu is more electronegative than Sr, such that the substitution lowers the Eu 4f5d-O 2p hybridized states. Consequently, the substitution reduces the energy of electron recombination between the valence and conduction bands, which is consistent with the red shift in the photoluminescence spectra. The presence of the newly formed hole states distributed over the O 2p states in the conduction band is strongly correlated with the emission intensity. The results and analyses demonstrate that Eu can be introduced to tailor the Eu-O hybridized states within the conduction band and change the route of recombination, suggesting that Eu is critically involved in light emission in these UV-induced orange-red emitting LED materials.",
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AU - Chan, Ting Shan

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AU - Chen, Yi Hauan

AU - Lu, Ying Rui

AU - Wu, Sheng Yun

AU - Ma, Yuan Ron

AU - Lin, Chun Che

AU - Liu, Ru Shi

AU - Chen, Jeng Lung

AU - Guo, Jinghua

AU - Lee, Jyh Fu

AU - Sheu, Hwo Shuenn

AU - Yang, Chun Chuen

AU - Chen, Chi Liang

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AB - The origin of light emission from newly discovered orange-red UV light emitting diodes, and their electronic properties are critical issues yet to be understood. In this study, X-ray absorption spectroscopy (XAS) and emission spectroscopy (XES) are utilized to examine the electronic structure of the Eu3+-doped Bi2SrTa2O9 system. While no significant change in the electronic structure is observed around the Bi and Ta sites, variation around the Eu and Sr atoms is observed, along with even more significant changes in the O 2p states in the conduction band. Upon UV irradiation, Eu-induced states within the conduction band are observed and found to shift to the conduction band minimum upon substitution of Sr with Eu. This phenomenon is the result of the creation by Eu of an excitable state and the fact that Eu is more electronegative than Sr, such that the substitution lowers the Eu 4f5d-O 2p hybridized states. Consequently, the substitution reduces the energy of electron recombination between the valence and conduction bands, which is consistent with the red shift in the photoluminescence spectra. The presence of the newly formed hole states distributed over the O 2p states in the conduction band is strongly correlated with the emission intensity. The results and analyses demonstrate that Eu can be introduced to tailor the Eu-O hybridized states within the conduction band and change the route of recombination, suggesting that Eu is critically involved in light emission in these UV-induced orange-red emitting LED materials.

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