14 results on '"Chih-Tao Chien"'
Search Results
2. Nanowire-based multifunctional antireflection coatings for solar cells
- Author
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Husnu Emrah Unalan, Waranatha Abeygunasekara, Chih-Tao Chien, Hang Zhou, Pritesh Hiralal, Jeremy J. Baumberg, Haider Butt, Abhishek Kumar, Niraj N. Lal, and Gehan A. J. Amaratunga
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chemistry.chemical_classification ,Materials science ,Organic solar cell ,business.industry ,Nanowire ,Nanotechnology ,Polymer ,engineering.material ,law.invention ,Contact angle ,chemistry ,Coating ,Superhydrophilicity ,law ,Solar cell ,engineering ,Optoelectronics ,General Materials Science ,Lotus effect ,business - Abstract
Organic (P3HT/PCBM) solar cells are coated with ZnO nanowires as antireflection coatings and show up to 36% enhancement in efficiency. The improvement is ascribed to an effective refractive index which results in Fabry-Perot absorption bands which match the polymer band-gap. The effect is particularly pronounced at high light incidence angles. Simultaneously, the coating is used as a UV-barrier, demonstrating a 50% reduction in the rate of degradation of the polymers under accelerated lifetime testing. The coating also allows the surface of the solar cell to self-clean via two distinct routes. On one hand, photocatalytic degradation of organic material on ZnO is enhanced by the high surface area of the nanowires and quantified by dye degradation measurements. On the other, the surface of the nanowires can be functionalized to tune the water contact angle from superhydrophilic (16°) to superhydrophobic (152°), resulting in self-cleaning via the Lotus effect. The multifunctional ZnO nanowires are grown by a low cost, low temperature hydrothermal method, compatible with process limitations of organic solar cells.
- Published
- 2014
3. Tunable Photoluminescence from Graphene Oxide
- Author
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Takeshi Fujita, Manishkumar Chhowalla, Shao Sian Li, Chih-Tao Chien, Goki Eda, Seiji Isoda, Hsin An Chen, Hisato Yamaguchi, I. Shen Chen, Kuei-Hsien Chen, Wei Jung Lai, Takashi Nemoto, Mingwei Chen, Chun-Wei Chen, Yun Chieh Yeh, and Li-Chyong Chen
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Materials science ,Graphene ,Tunable photoluminescence ,Oxide ,Nanotechnology ,General Medicine ,General Chemistry ,Catalysis ,law.invention ,chemistry.chemical_compound ,Scanning probe microscopy ,chemistry ,law ,Luminescence ,Graphene nanoribbons ,Graphene oxide paper - Published
- 2012
4. Graphene-Based Integrated Photovoltaic Energy Harvesting/Storage Device
- Author
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Di Yan Wang, Pritesh Hiralal, Chun-Wei Chen, Chia Chun Chen, I-Sheng Huang, Chih-Tao Chien, and Gehan A. J. Amaratunga
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Supercapacitor ,Materials science ,Organic solar cell ,Graphene ,Photovoltaic system ,Nanotechnology ,General Chemistry ,Capacitance ,Energy storage ,law.invention ,Biomaterials ,law ,Energy transformation ,General Materials Science ,Energy source ,Biotechnology - Abstract
Energy scavenging has become a fundamental part of ubiquitous sensor networks. Of all the scavenging technologies, solar has the highest power density available. However, the energy source is erratic. Integrating energy conversion and storage devices is a viable route to obtain self-powered electronic systems which have long-term maintenance-free operation. In this work, we demonstrate an integrated-power-sheet, consisting of a string of series connected organic photovoltaic cells (OPCs) and graphene supercapacitors on a single substrate, using graphene as a common platform. This results in lighter and more flexible power packs. Graphene is used in different forms and qualities for different functions. Chemical vapor deposition grown high quality graphene is used as a transparent conductor, while solution exfoliated graphene pastes are used as supercapacitor electrodes. Solution-based coating techniques are used to deposit the separate components onto a single substrate, making the process compatible with roll-to-roll manufacture. Eight series connected OPCs based on poly(3-hexylthiophene)(P3HT):phenyl-C61-butyric acid methyl ester (PC60 BM) bulk-heterojunction cells with aluminum electrodes, resulting in a ≈5 V open-circuit voltage, provide the energy harvesting capability. Supercapacitors based on graphene ink with ≈2.5 mF cm(-2) capacitance provide the energy storage capability. The integrated-power-sheet with photovoltaic (PV) energy harvesting and storage functions had a mass of 0.35 g plus the substrate.
- Published
- 2014
5. Photovoltaic and optoelectronic applications of large-area graphene-based electronics
- Author
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Shao Sian Li, Jeong-Yuan Huang, Kuei-Hsien Chen, Chih-Tao Chien, Kun-Hua Tu, Li-Chyong Chen, Manishkumar Chhowalla, and Chun-Wei Chen
- Subjects
chemistry.chemical_classification ,Photoluminescence ,Materials science ,Graphene ,business.industry ,Photovoltaic system ,Nanotechnology ,Polymer ,Chemical vapor deposition ,law.invention ,chemistry ,PEDOT:PSS ,law ,Electrode ,Optoelectronics ,Electronics ,business - Abstract
Summary form only given. In this talk, we would like to present the applications of graphene-based materials on large-area photovoltaic and optoelectronic devices. Chemically derived graphene-oxide (GO) from solution processes or epitaxial graphene obtained from chemical vapor deposition (CVD) have been demonstrated to replace the ITO electrode. GO could be also a simple solution processable alternative to PEDOT:PSS as the effective hole transport and electron blocking layer in polymer photovoltaics, suggesting that future polymer solar-cell devices could be "all-carbon". In addition, photoluminescence of GO and reduced-GO will be demonstrated. The tunablity of PL emission from red to blue colors offers a potential to use graphene-based materials on solution-processable optoelectronic devices for full-color display and lighting applications.
- Published
- 2010
6. Effects of bifunctional linker on the optical properties of ZnO nanocolumn-linker-CdSe quantum dots heterostructure
- Author
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Jih-Jen Wu, Wei-Fang Su, Chih-Tao Chien, I-Shuo Liu, Hsuieh-Chung Liao, Yang-Fang Chen, Tsung-Wei Zeng, Chun-Wei Chen, Daniel Kwan-Pang Wong, and Kuo-Tung Huang
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business.industry ,Heterojunction ,Nanotechnology ,Acceptor ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Biomaterials ,Electron transfer ,chemistry.chemical_compound ,Colloid and Surface Chemistry ,chemistry ,X-ray photoelectron spectroscopy ,Quantum dot ,Optoelectronics ,Bifunctional ,business ,Spectroscopy ,Linker - Abstract
We study the effects of bifunctional linker on the optical properties of ZnO nanocolumn-linker-CdSe quantum dots heterostructure. The CdSe quantum dots are anchored on the surface of ZnO nanocolumns through either aliphatic linker of 3-aminopropyl trimethoxysilane (APS) or aromatic linker of p-aminophenyl trimethoxysilane (APhS). X-ray photoelectron spectroscopy is used to confirm the bifunctional linker bound onto CdSe quantum dots and onto the ZnO nanocolumns. The TEM study reveals a CdSe quantum dot shell of about 15 nm coated on the ZnO nanocolumns. The photoluminance (PL) spectroscopy and time-resolved PL spectroscopy of ZnO nanocolumn-linker-CdSe quantum dots reflects that the photo-induced electron transfer across the interface of ZnO and CdSe through the aromatic APhS is more efficient than the aliphatic APS. This study demonstrates that through the usage of appropriate surface linker, the charge transfer rate across the interfaces of donor/acceptor (D/A) heterostructure can be improved for potential photovoltaic cell applications.
- Published
- 2010
7. Incorporating semiconducting single-walled carbon nanotubes as efficient charge extractors in organic solar cells
- Author
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Gehan A. J. Amaratunga, Chih-Tao Chien, Abhishek Kumar, Lilantha Samaranayake, Waranatha Abeygunasekara, Veranja Karunaratne, Pritesh Hiralal, and Andrew J. Flewitt
- Subjects
Materials science ,Physics and Astronomy (miscellaneous) ,Equivalent series resistance ,Organic solar cell ,Energy conversion efficiency ,Nanotechnology ,Carbon nanotube ,Orders of magnitude (numbers) ,Polymer solar cell ,law.invention ,Chemical engineering ,law ,Solar cell ,Current density - Abstract
We report on the improvement of power conversion efficiency (PCE) of PTB7/PC70BM solar cells by the addition of small quantities (0.02%–0.04%) of pristine single-walled carbon nanotubes (SWNTs) in the active-layer. SWNTs and purified semiconducting SWNTs (S-SWNTs) were added in quantities, which is 2 orders of magnitude lower than previously reported value and resulted in a reduction in the series resistance of the solar cell with minor changes on the shunt resistance. On addition of purified S-SWNT, the PCE of air measured devices enhanced by 29% from 4.9% to 6.3%, with short-circuit current density (Jsc) improving from 12.1 mA/cm2 to 14.4 mA/cm2 and a fill factor improvement from 54% to 61%. In addition, the role of processing additive N-Methyl-2-pyrrolidone, which acts as a SWNT dispersant, is also investigated. A single diode model of a solar cell is used to extract the cell parameters and understand the effect of SWNTs. Based on experimental data and it's fitting to the single diode model, we propose...
- Published
- 2015
8. Incorporating semiconducting single-walled carbon nanotubes as efficient charge extractors in organic solar cells.
- Author
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Abeygunasekara, Waranatha L., Hiralal, Pritesh, Samaranayake, Lilantha, Chih-Tao Chien, Kumar, Abhishek, Flewitt, Andrew J., Karunaratne, Veranja, and Amaratunga, Gehan A. J.
- Subjects
SOLAR cells ,SINGLE walled carbon nanotubes ,SEMICONDUCTORS ,EXTRACTION apparatus ,ENERGY conversion - Abstract
We report on the improvement of power conversion efficiency (PCE) of PTB7/PC
70 BM solar cells by the addition of small quantities (0.02%-0.04%) of pristine single-walled carbon nanotubes (SWNTs) in the active-layer. SWNTs and purified semiconducting SWNTs (S-SWNTs) were added in quantities, which is 2 orders of magnitude lower than previously reported value and resulted in a reduction in the series resistance of the solar cell with minor changes on the shunt resistance. On addition of purified S-SWNT, the PCE of air measured devices enhanced by 29% from 4.9% to 6.3%, with short-circuit current density (JSC ) improving from 12.1mA/cm² to 14.4 mA/cm² and a fill factor improvement from 54% to 61%. In addition, the role of processing additive N-Methyl-2-pyrrolidone, which acts as a SWNT dispersant, is also investigated. A single diode model of a solar cell is used to extract the cell parameters and understand the effect of SWNTs. Based on experimental data and it's fitting to the single diode model, we propose that S-SWNT improve the transport and extraction of photogenerated charges within the solar cell device. [ABSTRACT FROM AUTHOR]- Published
- 2015
- Full Text
- View/download PDF
9. Polarization-dependent confocal Raman microscopy of an individual ZnO nanorod
- Author
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Chun-Wei Chen, Wei-Fang Su, Hung Hsien Yang, Yang-Fang Chen, Chauo Sung Lin, Ming-Chung Wu, Jih-Jen Wu, and Chih-Tao Chien
- Subjects
Materials science ,Microscope ,Physics and Astronomy (miscellaneous) ,business.industry ,Scattering ,Phonon ,law.invention ,Condensed Matter::Materials Science ,symbols.namesake ,Optics ,law ,Microscopy ,symbols ,Optoelectronics ,Nanorod ,business ,Anisotropy ,Raman spectroscopy ,Raman scattering - Abstract
In this study, polarized-Raman scattering measurements of an individual ZnO nanorod were carried out by using a confocal microscope together with a high-resolution piezoelectric stage. A predominant A1 (TO) mode at 378cm−1 in the parallel polarization (E∥) configuration and a predominant E2 (high) mode at 438cm−1 in the perpendicular polarization (E⊥) configuration demonstrate the strong polarization dependent Raman scattering signals of an individual ZnO nanorod. The Raman intensity images of the individual ZnO nanorods with different orientation configurations can also be obtained, which reflect the interplay between the local phonon behavior and geometric anisotropy.
- Published
- 2008
10. Enhancing photoluminescence quenching and photoelectric properties of CdSe quantum dots with hole accepting ligands
- Author
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Sz-Chian Liou, Yun-Yue Lin, Chih-Tao Chien, Chun-Wei Chen, Wei-Fang Su, Yang-Fang Chen, I-Shuo Liu, and Hsi-Hsing Lo
- Subjects
Photocurrent ,Photoluminescence ,Ligand ,Thiophenol ,Analytical chemistry ,General Chemistry ,Photochemistry ,Acceptor ,chemistry.chemical_compound ,chemistry ,Quantum dot ,Materials Chemistry ,Molecule ,Trioctylphosphine oxide - Abstract
CdSe quantum dots have been encapped with aromatic ligands: α-toluenethiol, thiophenol, and p-hydroxythiophenol to enhance the photoluminescence (PL) quenching and photoelectric properties of the quantum dots. The aromatic ligand capped CdSe quantum dots are prepared through ligand exchange with trioctylphosphine oxide (TOPO) capped CdSe quantum dots. The XPS surface chemistry analysis and elemental analysis has confirmed the success of ligand exchange from TOPO to aromatic ligands. Both XRD and HRTEM-SAED studies indicate the crystalline structure of CdSe quantum dots not only remains but is also improved by the ligand exchange of TOPO with thiol molecules. Time resolved PL decay measurements indicate thiophenol and p-hydroxythiophenol ligands effectively quench the emission and have much shorter PL lifetimes than that of TOPO and that of α-toluenethiol. Thus, both thiophenol and p-hydroxythiophenol can act as an effective acceptor for photogenerated holes through aromatic π-electrons. Thiophenol also exhibits good charge transport behavior showing a 10-fold increase in short circuit current density (Isc) as compared with TOPO in the photocurrent study of fabricated photovoltaic devices.
- Published
- 2008
11. Structural and optical properties of single crystal Zn1−xMgxO nanorods—Experimental and theoretical studies
- Author
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Jih-Jen Wu, Chao-Sung Lin, Kuei-Hsien Chen, Hsuen-Han Chiang, Chen-Hao Ku, Chun-Wei Chen, Chih-Tao Chien, Li-Chyong Chen, Yu-Sheng Chang, and Ta-Ya Chu
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Delocalized electron ,Crystallography ,Photoluminescence ,Materials science ,Chemical physics ,Exciton ,Density of states ,General Physics and Astronomy ,Ionic bonding ,Nanorod ,Single crystal ,Blueshift - Abstract
Structural and optical properties of single crystal Zn1−xMgxO nanorods (0≤x≤0.17) are studied experimentally and theoretically. Structural analyses indicate that the nanorods grown on Si substrates are oriented in the c-axis direction and the nanorods possess the single-crystalline hexagonal structure with the Mg incorporated within the ZnO nanorods by means of substituting Zn. A blueshift of the near-band edge emission in the photoluminescence spectra by increasing Mg content is observed. Two distinct emission bands are found in the photoluminescence spectra; one is mainly attributed to the delocalized exciton recombination and the other is originating from localized excitons due to the incorporation of foreign impurity of Mg. Enhanced exciton localization with increasing Mg content in Zn1−xMgxO nanorods is mainly due to large ionic characters of Mg-O bonding. Structural stability, band structures, projected density of states, and charge distribution in various Zn1−xMgxO alloy compounds were further inve...
- Published
- 2007
12. Electrodeposition of Nickel-Phosphorus Alloy from Sulfamate Baths with Improved Current Efficiency
- Author
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F. J. Chen, Chih-Tao Chien, W. C. Chung, P. L. Lin, Chun-Ying Lee, and Chao-Sung Lin
- Subjects
Renewable Energy, Sustainability and the Environment ,Phosphorus ,Inorganic chemistry ,Alloy ,chemistry.chemical_element ,engineering.material ,Condensed Matter Physics ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,chemistry.chemical_compound ,Nickel ,chemistry ,Plating ,Materials Chemistry ,Electrochemistry ,engineering ,Current (fluid) ,Phosphorous acid ,Electroplating ,Current density - Abstract
In this study, nickel-phosphorus (Ni-P) deposits were electroplated from the nickel sulfamate bath containing phosphorous acid using a pulse current, with emphasis on the effect of current density, duty cycle, and frequency of the pulse current. Experimental results show that both the deposit phosphorus content and current efficiency were substantially enhanced by employing the pulse current, preferentially at low duty cycles. The underlying difference for the dc and pulse currents on the effect of deposit phosphorus content and current efficiency can be explained by the detailed half-reactions relevant to incorporation of phosphorus into Ni-P alloys. Less variation in surface proton, Ni 2+ and H 3 PO 3 concentration due to the diffusion recovery during the time off of a pulse current is believed to play an important role in the improvement of the plating process.
- Published
- 2006
13. Polarization-dependent confocal Raman microscopy of an individual ZnO nanorod.
- Author
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Chih-Tao Chien, Ming-Chung Wu, Chun-Wei Chen, Hung-Hsien Yang, Jih-Jen Wu, Wei-Fang Su, Chauo-Sung Lin, and Yang-Fang Chen
- Subjects
- *
POLARIZATION (Electricity) , *RAMAN effect , *LIGHT scattering , *ZINC oxide , *PIEZOELECTRIC devices , *ANISOTROPY - Abstract
In this study, polarized-Raman scattering measurements of an individual ZnO nanorod were carried out by using a confocal microscope together with a high-resolution piezoelectric stage. A predominant A1 (TO) mode at 378 cm-1 in the parallel polarization (E∥) configuration and a predominant E2 (high) mode at 438 cm-1 in the perpendicular polarization (E⊥) configuration demonstrate the strong polarization dependent Raman scattering signals of an individual ZnO nanorod. The Raman intensity images of the individual ZnO nanorods with different orientation configurations can also be obtained, which reflect the interplay between the local phonon behavior and geometric anisotropy. [ABSTRACT FROM AUTHOR]
- Published
- 2008
- Full Text
- View/download PDF
14. Photovoltaic and optoelectronic applications of large-area graphene-based electronics.
- Author
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Chun-Wei Chen, Shao-Sian Li, Kun-Hua Tu, Chih-Tao Chien, Jeong-Yuan Huang, Kuei-Hsien Chen, Li-Chyong Chen, and Chhowalla, M.
- Published
- 2010
- Full Text
- View/download PDF
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