Enhancing optical absorption in visible light of ZnO co-doped with europium and promethium by first-principles study through modified Becke and Johnson potential scheme

Hachimi, A.G. El; Ne, M. L. Ould; Yousfi, Abdellah; Benyoussef, A.; Kenz, A. El

doi:10.1016/j.jre.2018.08.011

Cited by 18 publications

(10 citation statements)

References 35 publications

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“…To enhance the photocatalytic efficiency, various synthesis methods and surface modifications (doping, composite, and deposition) have been adopted to change the crystal structure, size, morphology, and bandgap [13]. Metal doping can effectively promote the visible light harvesting ability of catalysts [14][15][16][17][18][19][20]. Yttrium (Y) is an environmentally-friendly and abundant rare earth (RE) element [21].…”

Section: Introductionmentioning

confidence: 99%

First-Principles Calculations of the Electronic Structure and Optical Properties of Yttrium-Doped ZnO Monolayer with Vacancy

Wang

Liu

et al. 2020

Materials

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The electronic structures and optical characteristics of yttrium (Y)-doped ZnO monolayers (MLs) with vacancy (zinc vacancy, oxygen vacancy) were investigated by the first-principles density functional theory. Calculations were performed with the GGA+U (generalized gradient approximation plus U) approach, which can accurately estimate the energy of strong correlation semiconductors. The results show that the formation energy values of Y-doped ZnO MLs with zinc or oxygen vacancy (VZn, VO) are positive, implying that the systems are unstable. The bandgap of Y-VZn-ZnO was 3.23 eV, whereas that of Y-VO-ZnO was 2.24 eV, which are smaller than the bandgaps of pure ZnO ML and Y-doped ZnO MLs with or without VO. Impurity levels appeared in the forbidden band of ZnO MLs with Y and vacancy. Furthermore, Y-VZn-ZnO will result in a red-shift of the absorption edge. Compared with the pure ZnO ML, ZnO MLs with one defect (Y, VZn or VO), and Y-VZn-ZnO, the absorption coefficient of Y-VO-ZnO was significantly enhanced in the visible light region. These findings demonstrate that Y-VO-ZnO would have great application potential in photocatalysis.

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Section: Introductionmentioning

confidence: 99%

First-Principles Calculations of the Electronic Structure and Optical Properties of Yttrium-Doped ZnO Monolayer with Vacancy

Wang

Liu

et al. 2020

Materials

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“…A few theoretical studies on Eu-doping in ZnO can be found in the literature. (64)(65)(66)(67)(68)(69)(70) Yet, to the best of our knowledge, the possibility of Eu-oxide cluster formation, as observed here, has not been considered so far. Most of these theoretically calculated structures considered single atom doping,(64-68) isovalent doping, (69,70) or doping associated with point defects at Zn sites (substitutional).…”

Section: Dft Modelling Of the Zno:eu Structurementioning

confidence: 75%

Molecular sized Eu-oxide clusters in defining optical properties in crystalline ZnO nanosponges

Mukherjee

Katea

Rodrigues

et al. 2021

Preprint

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The detailed structure of ZnO doped with 5 at.% (metal) of the large aliovalent Eu3+-ions was investigated using EXAFS to describe the local Eu and Zn coordination. The microstructure, crystalline phases, contents and ZnO unit-cell parameters for the ZnO:5%Eu sponges synthesised at 200 to 900 oC were obtained by XRD, SEM, and TEM analysis. XRD showed peaks solely of h-ZnO for the 600 oC sample, while heating at 700 oC and higher caused phase separation into h-ZnO:Eu and c-Eu2O3. XRD showed a close to zero increase in ZnO unit cell-volume of ca. 0.4 vol%, compared to un-doped ZnO for the non-phase separated, clean oxide made at 600 oC. The Zn EXAFS data showed an almost intact local ZnO structure. The Eu EXAFS showed an unusually low coordination number (CN) of ca. 5 for the 200-600 oC samples, while the CN increased for higher temperatures, in concert with the formation of c-Eu2O3. 23 DFT-generated theoretical ZnO structures containing Eu-clusters built from 1 to 4 Eu3+-Zn2+-vacancy- Eu3+ pairs were compared with the experimental data. The lowest formation energies and ZnO unit-cell volume increase versus un-doped ZnO (0.6-0.7 vol%), were obtained when combining two or four Eu3+-Zn2+-vacancy- Eu3+ pairs into Eu4 and Eu8 clusters showing an average Eu CN of ca. 5. These theoretically determined lowest energy structures were all in good agreement with the experimental results obtained by EXAFS and XRD. Photoluminescence excitation and emission spectra performed on the ZnO:5at%Eu sponges obtained at various temperatures, showed strong quenching of the characteristic Eu3+ transitions for samples obtained at 600 and 800 °C, most likely due to changes in the ZnO defect states, which are crucial for Eu3+ excitation, and due to self-quenching upon Eu clustering and c- Eu2O3 phase separation. Thus, the optical data further supported Eu clustering found by EXAFS, DFT and XRD techniques, corroborating structure-property relationships in these materials. Overall, as far as we can find, the findings reported herein point to a doping structure very different from those previously proposed in the literature. It demonstrates that the semiconductor ZnO can host molecular-sized clusters of metal-oxides, very dissimilar to ZnO.

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“…ε 2 (ω) is directly related to the electronic band structure. It is calculated by summing all transitions from occupied states to unoccupied states using the well-known relation [34]:…”

Section: Optical Studiesmentioning

confidence: 99%

“…The relation between the absorption coefficient ⍺, the incident photon energy hν and the optical energy gap E g can be established by using Tauc's relationship mentioned above [34]:…”

Section: Optical Band Gap Determinationmentioning

confidence: 99%

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Theoretical investigation of electronic, optical and thermoelectric properties of tellurium doped barium titanate (BTO) through modified Becke – Johnson exchange potential

Ziati

Ez‐Zahraouy

2021

Optik

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Enhancing optical absorption in visible light of ZnO co-doped with europium and promethium by first-principles study through modified Becke and Johnson potential scheme

Cited by 18 publications

References 35 publications

First-Principles Calculations of the Electronic Structure and Optical Properties of Yttrium-Doped ZnO Monolayer with Vacancy

First-Principles Calculations of the Electronic Structure and Optical Properties of Yttrium-Doped ZnO Monolayer with Vacancy

Molecular sized Eu-oxide clusters in defining optical properties in crystalline ZnO nanosponges

Theoretical investigation of electronic, optical and thermoelectric properties of tellurium doped barium titanate (BTO) through modified Becke – Johnson exchange potential

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