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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
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Jiramitmonkon, Kanpitcha
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Piyakulawat, Phimwipha
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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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Effects of tetramethylene sulfone solvent additives on conductivity of PEDOT:PSS film and performance of polymer photovoltaic cells
(2013-01-01)
Keawprajak, Anusit
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Koetniyom, Wantana
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Piyakulawat, Phimwipha
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Jiramitmongkon, Kanpitcha
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Pratontep, Sirapat
A solvent additive in PEDOT:PSS solution is one of many methods to improve the conductivity of the poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) films. We explore a new type of the solvent additive, namely tetramethylene sulfone (TMS), for the fabrication of the PEDOT:PSS conductive layer in the ITO/PEDOT:PSS/P3HT:PCBM/TiO<inf>x</inf>/Al polymer photovoltaic cells, in comparison to a more common dimethyl sulfoxide (DMSO) solvent additive. At optimal conditions, the TMS additive at 10 wt.% has been found to enhance the conductivity of pristine PEDOT:PSS films from 0.04 S/cm up to approximately 189 S/cm, compared with the highest conductivity for the case of the DMSO additive at 15 wt.% of 117 S/cm. Possible mechanisms of this conductivity enhancement, relating to the polymer conformation and the film morphology, have been investigated by Raman spectroscopy, X-ray diffraction, atomic force microscopy, and transmission electron microscopy. The performance of the polymer photovoltaic cells fabricated with the solvent additives PEDOT:PSS films follows a similar trend to the conductivity of the films as a function of the additive concentration. The additives mainly lead to greater short circuit current density (J<inf>sc</inf>) of the photovoltaic cells. The highest power conversion efficiency (PCE) of 2.24% of the device has been obtained with the 10 wt.% TMS additive of, compared to the PCE of 1.48% for the standard device without solvent additive. © 2012 Elsevier B.V. All rights reserved.
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Heavy metal detection by electrochemical electronic tongue with poly(thiophene)-metal oxide nanoparticle composite electrodes
(2011-12-01)
Saeteaw, Kanjana
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Tumcharern, Gamolwan
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Piyakulawat, Phimwipha
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Asawapirom, Udom
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Porntheeraphat, Supanit
Rapid monitoring methods of heavy metals in water are in great demand for industrial environmental managements. This work aims to develop a heavy metal sensing device based on an electrochemical electronic tongue using a hybrid composite of metal oxide nanoparticles and conductive polymer as the working electrodes. The electrodes were prepared by drop-casting colloidal mixtures of Regioregular poly(3-hexylthiophene) (P3HT) and metal oxide nanoparticles (ZnO or TiO <inf>2</inf>) in chloroform onto a fluorine-doped tin oxide (FTO) glass. Optical microscopy measurements reveal some microstructural organization of the metal oxide-P3HT composite films on the electrodes, in comparison to a smooth P3HT film. Cyclic voltammetry (CV) measurements using bare FTO, P3HT, P3HT/ZnO and P3HT/TiO <inf>2</inf> electrodes were performed on aqueous solutions of various metal acetates at the concentration of 0.01M. The Principal Component Analysis (PCA) was applied to the CV results to obtain the classification of the data from the various metal salt solutions. The PCA score plot exhibits a clear separation of the data groups of different heavy metals, with the highest distinction between zinc and lead. The PCA loading plot confirms that the different electrochemical nature of the various electrodes is responsible for such distinctive classification. Further work is to examine the capability of the electrochemical electronic tongues for semi-quantitative analyses of the metal salt concentration. © 2011 IEEE.

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