First-Principles Calculations On Solgel Zinc Oxide Nanoparticles Optoelectronic Properties
An efficient diagnostic between experimental and theoretical calculation is essential to ensure the synergy between these two approaches. This study made attempt to use structural input from experimental in the theoretical framework. Initially, ZnO nanoparticles were synthesized by sol-gel method...
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| Main Author: | |
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| Format: | Thesis |
| Language: | English |
| Published: |
2018
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| Subjects: | |
| Online Access: | http://eprints.usm.my/47338/1/First-Principles%20Calculations%20On%20Solgel%20Zinc%20Oxide%20Nanoparticles%20Optoelectronic%20Properties.pdf |
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| Summary: | An efficient diagnostic between experimental and theoretical calculation is
essential to ensure the synergy between these two approaches. This study made
attempt to use structural input from experimental in the theoretical framework.
Initially, ZnO nanoparticles were synthesized by sol-gel method at different aging
time. The phase and structural analyses confirmed the formation of hexagonal
wurtzite ZnO structure at which sample aged at 36 h showed highest crystallinity and
gave the best visual fit in Rietveld analysis. Morphological observation revealed
spherical nanoparticles were formed at aging time higher than 6 h while only small
variation in energy band gap recorded between 3.08 – 3.12 eV. The
photoluminescence spectra revealed a green emission due to oxygen vacany. In firstprinciples
calculation, the ZnO unit cell was built based on structural parameter from
Rietveld analysis in order to provide a bridge with experimental study. Several
exchange-correlation functional including LDA, GGA-PBE, GGA-PBESol, LDA+U,
GGA-PBE+U and GGA-PBESol+U were tested. The GGA-PBE+U (Ud,Zn = 10 eV
and Up,O = 6.1 eV) showed lowest lattice deviation and successfully reproduced the
experimental band gap. ZnO supercell structure with oxygen vacancy showed that
defect state were more delocalized and appeared at 1.90 eV from top of conduction
band. This position was close to the photon energy released due to recombination of
electron (2.06 eV) as observed in luminescence spectra. The results are beneficial in
designing photoanode material in solar cell that will enhance visible light absorption. |
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