Structural and optical properties of graphene-based zinc selenide composites prepared via microwave-assisted hydrothermal method for photovoltaic and photonics application
The global energy demands will more than supply by the year 2040. In order to resolve this problem, the energy should be generated by using renewable source or reduce the energy consumption. Zinc selenide (ZnSe) has been widely used in applications such as LED, solar cell and other. There were r...
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| Main Author: | |
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| Format: | Thesis |
| Language: | English |
| Published: |
2019
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| Subjects: | |
| Online Access: | http://psasir.upm.edu.my/id/eprint/83695/1/FS%202019%2033%20-%20ir.pdf |
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| Summary: | The global energy demands will more than supply by the year 2040. In order to
resolve this problem, the energy should be generated by using renewable
source or reduce the energy consumption. Zinc selenide (ZnSe) has been
widely used in applications such as LED, solar cell and other. There were
researches on enhancing ZnSe properties by doping or mixing with other
materials but there is not much reports on forming graphene-based ZnSe
composite. In this research, graphene-based zinc selenide composites were
synthesized via microwave-assisted hydrothermal method. Microwave-assised
hydrothermal method was employed as it can greatly reduce the energy
consumption, cost and time. Home made hydrothermal autoclave was used to
charge the precursor and heated in the microwave oven. Through this method,
the energy consumption, cost and reaction time were drastically reduced by
99%. The optimized condition to synthesis graphene-based ZnSe composite
was using 0.100 mole of NaOH, 2ml of diethanolamine (surfactants) heated for
3 minutes under 700 W microwave irradiation power. The structural,
morphological and optical properties of graphene-based zinc selenide
composites were then characterized with X-Ray Diffraction (XRD), Fourier
Transform Infrared Spectroscopy (FTIR), Raman Spectroscopy, Field Emission
Scanning Electron Microscope (FESEM), Atomic Force Microscope (AFM),
Diffuse Reflectance Spectroscopy (DRS) and Photoluminescence (PL)
Spectroscopy. For ZnSe/GO and ZnSe/GNP composites, cubic ZnSe was
grown on the GO or GNP sheets which was observed in the AFM image. The
spherical shape of pure ZnSe changed to nanoflakes as GO or GNP was
added in as precursor. The purity of ZnSe formed was reduced from 100 % of
ZnSe to 86.3 % as concentration of GO or GNP added was higher. The
electron density in the sample was then determined via Fourier mapping. The
electron density occupied the empty spaces within the cubic structure of ZnSe as GO or GNP was added. From Raman spectra, it can be confirmed that
ZnSe/GO and ZnSe/GNP composites were formed. The intensity ratio between
D band and G band (Id/Ig) was ~1 for ZnSe/GO composites and ~0.3 for
ZnSe/GNP composites. The chemical bonding of GO and GNP was
determined via FTIR technique where C=C, C-O, CH3, C-H and –COO- bonding
were found in ZnSe/GO and ZnSe/GNP composite. The optical band gap of
ZnSe is 2.64 eV. The band gap changed to 2.62 eV and 3.02 eV as GO and
GNP were added, respectively. The sample was excited by a wavelength of
290 nm where the PL emission peak for all samples were centered at ~466 nm.
The samples were tested on the photovoltaic and photonic applications. The
solar efficiency was increased from 0.19% (pure ZnSe) to 1.61 % when GO
was added and 11.88 % when GNP is added. In addition, it has been proved
that graphene-based ZnSe composite managed to generate femtosecond
pulse of ~540 fs which can become a promising materials in photonics
application such as micro- or nano-machining technology, non-linear imaging
and microscopy and micro- and nano-surgery technology. Modification of ZnSe
to form ZnSe/GO and ZnSe/GNP composite will change the electron density,
morphology and optical properties. This research provides a fundamental
knowledge to support the properties required for photovoltaic and photonics
application. |
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