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Author: search.filters.author.Pratontep, SirapatSubject: search.filters.subject.Zinc oxide

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    Photoresponse of composites of zinc oxide and poly(3-hexythiophene) under selective UV and white-light illumination
    (2016-12-01)
    Pattamang, Pattaraluck
    ;
    Jiramitmonkon, Kanpitcha
    ;
    Piyakulawat, Phimwipha
    ;
    Asawapirom, Udom
    ;
    Tantisantisom, Kittitpong
    We investigate charge transport in UV sensing devices based on organic-inorganic semiconductor composites with the metal-semiconductor-metal (MSM) structure. Composite materials of zinc oxide (ZnO) nanoparticles and poly(3-hexylthiophene) (P3HT) were prepared by drop-casting their colloidal mixture in chloroform onto low-cost interdigitated copper electrodes. The current-voltage characteristics of the devices were investigated under both dark and illuminated conditions in the UV–visible range. The highest photoresponse was observed for an optimal P3HT:ZnO ratio of 1:8 w/w in the wavelength range between 310 and 380 nm. The dynamic response was investigated by pulsing a 365 nm UV light with a long period to reveal the response time of 4 s and the recovery time of less than 1 s. The photoresponse of the materials was also investigated for a shorter period of UV pulsing, using a rotating chopper. The response time and recovery time for the short UV pulse were found to be approximately 20 m and 25 m, respectively. The dual response times should stem from the presence of two types of semiconductor materials, namely ZnO with a high electron mobility and P3HT with a moderate hole mobility. To probe the charge generation and transport mechanisms, we further investigate the photoresponse using UV pulsing under background white light of different intensities, and vice versa. The background white light was found to deteriorate the UV photoresponse of the materials. On the other hand, the background UV illumination produced an anomalous photoresponse pattern with the white light pulsing. Understanding the charge transport mechanisms for composite materials is highly important for future applications in low-cost UV sensors and tunable optoelectronic devices.
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    Performance improvement of zinc oxide photoanode-based dye-sensitized solar cells by multi-walled carbon nanotube
    (2010-11-01)
    Chindaduang, Anon
    ;
    Duangkaew, Pattasuda
    ;
    Pratontep, Sirapat
    ;
    Tumcharern, Gamoiwan
    Unique electrical and surface-to-volume properties of carbon nanotubes have made these conductive molecules highly attractive in many applications. In this work, the influence of multi-walled carbon nanotubes into a zinc oxide active layer of dye-sensitized zinc oxide solar cell has been investigated. With this method, a significant improvement in the performance of the solar cell has been achieved. Compared to the typical zinc oxide photoelectrochemical cells, the photocurrent- voltage characteristics of the fabricated cell containing 0.05 percent by weight of carbon nanotubes in the metal oxide film displayed a higher short-circuit photocurrent, consequently caused an increase of the solar-to-electricity conversion efficiency by a factor of approximately 1.4. Further increase of the conductive carbon material resulted in a decrease of the energy conversion of the photovoltaic cell. The enhancement of the energy conversion at this optimum carbon nanotube loading may be attributed to the dye-adsorption ability and the electrochemical activity of the composite photoanodes. The fabricated photovoltaic cells with the highest efficiency exhibited the maximum dye adsorption intensity and the minimum charge transfer resistance, as measured by ultraviolet-visible spectroscopy and electrochemical impedance spectroscopy, respectively . Copyright © 2010 American Scientific Publishers.
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    Growth and characterization of zinc oxynitride thin films by reactive gas-timing RF magnetron sputtering
    (2008-01-22)
    Klaitabtim, Don
    ;
    Pratontep, Sirapat
    ;
    Nukeaw, Jiti
    Nitrogen-doped zinc oxide (N:ZnO) films on glass substrates have been prepared by the reactive gas-timing rf magnetron sputtering of ZnO targets in a mixture of argon and nitrogen gases. Using this gas-timing technique, N:ZnO films were produced without any substrate heating. The nitrogen partial pressure during the sputtering process was periodically controlled by an on-off sequence. The structural and optical properties of the fabricated films were analyzed by X-ray diffraction (XRD) and optical absorption spectroscopy, respectively. The nitrogen composition of the N:ZnO films was quantified by X-ray photoelectron spectroscopy (XPS). In this study, we focused on investigating the effects of the nitrogen flow rate and the rf power on the structural properties, the nitrogen doping efficiency, and the optical band gap of N:ZnO films. A slight shift in the optical band gap to a higher energy was found when the nitrogen flow rate was increased or when the rf power was decreased. This coincides with an improvement in the crystallinity of the films. Gas-timing rf magnetron sputtering deposition is a simple method of fine-tuning material properties by slight modifications to the existing sputtering technique. © 2008 The Japan Society of Applied Physics.