Browsing by Author "Liao, Hung-Chou"

Now showing 1 - 8 of 8

A nanoporous optically transparent CdS-pHEMA hybrid with high optical sensing capability to dielectric liquids
(2009-03-04)
Liao, Hung-Chou
;
Liu, Yen-Yu
;
Chen, San-Yuan
;
Liu, Dean-Mo
;
材料科學與工程學系
A hydrogel-based functional hybrid with highly uniformly dispersed nanoparticulate CdS semiconductors is proposed. The hybrid is synthesized using an in situ polymerization following an in situ chemical reduction, where the resulting particle size and the distribution of CdS nanocrystals (NCs) can be narrowly manipulated. The hybrids, containing a relatively small amount of the CdS NCs, exhibit a pronounced photoluminescence spectrum shift when in contact with a number of dielectric liquids and such a pronounced dielectric-confinement effect has been experimentally verified and modeled in this study. The sensing capability of the hybrids with respect to dielectric liquids or molecules can be optically characterized and varied depending upon the intensity of the dielectric environment surrounding the hybrids. This work suggests that the transparent, nanoporous CdS-pHEMA hybrids can be used as highly efficient optical sensing materials.
Annealing Effect on Photovoltaic Performance of Hybrid P3HT/In-Situ Grown CdS Nanocrystal Solar Cells
(2011)
Liao, Hung-Chou
;
Chantarat, Naratip
;
Chen, San-Yuan
;
Peng, Cheng-Hsiung
;
材料科學與工程學系
The CdS nanocrystals with different aspect ratios (ARs) can be synthesized directly in the presence of conjugated polymer poly(3-hexylthiophene-2,5-diyl) (P3HT). The UV-vis spectra of the composite films show a blue shift of the pi-pi* transition band with an increasing aspect ratio (AR) of the CdS nanocrystals, which was attributed to the destruction of the ordered structure of polymer chains as supported by PL measurements. Atomic force microscope measurements on P3HT/CdS film also demonstrate the aggregation of CdS nanocrystal in the P3HT matrix is more apparent for the CdS nanocrystals of AR 4 than that of AR 16, indicating a stronger interaction between P3HT and CdS for a larger AR (16), which is favorable for the network structure and formation of percolation paths to increase the transport properties of the P3HT/CdS solar cells. Therefore, a higher power conversion efficiencies (PCE) up to 2.95% can be obtained for the in-situ-grown P3HT/CdS with AR 16 upon annealing treatment at 160 degrees C for 60 min. (C) 2011 The Electrochemical Society. [DOI: 10.1149/1.3585668] All rights reserved.
Fabrication and Characterization of Mg-Doped ZnO Nanorod Arrays
(2010-07-01)
Liao, Hung-Chou
;
Chen, San-Yuan
;
Peng, Cheng-Hsiung
;
Lin, Chin-Ching
;
Cheng, Syh-Yuh
Photoelectronic characteristics are investigated in well-aligned MgO-coated ZnO nanorods (MgO/ZnO nanocables) grown on Si substrates buffered with ZnO film at a low temperature by solution techniques. Transmission electron microscopy shows that a rough surface was observed for the MgO-coated ZnO nanorods due to deposition of MgO nanoparticles on the surface of the ZnO nanorods. However, after annealed at high temperatures, the surface of the MgO-coated ZnO nanorods was flattened to form Mg-doped ZnO nanorods. Photoluminescence spectra of Mg-doped ZnO nanorods displayed a blue shift of the near-band-edge emission with increasing annealing temperature indicative of an increase in the band gap of the MgZnO alloy due to diffusion of the Mg atoms into the ZnO nanorods. In contrast, no blue shift was detected for the samples annealed in H(2)/N(2) (5%/95%) reduction atmosphere but a blue emission was detected at 800 degrees C, indicating that MgO diffusion process may produce a new luminescent center to emit the blue emission in H(2)/N(2) reduction atmosphere.
High electron injection structure in hybrid solar cells
(2008)
Liao, Hung-Chou
;
Chen, San-Yuan
;
Lin, Chin-Ching
;
Cheng, Syh-Yuh
;
材料科學與工程學系
We evaluate an ordered organic-inorganic solar cell architecture based on CdS QD-decorated ZnO nanorod arrays encased in the hole-conducting polymer Poly(3-hexylthiophene-2,5-diyl) (P3HT). In this work, CdS quantum dot with different sizes were attached to the surface of the nanorods capped with mercaptopropionic acid. The results show that the CdS QDs on the ZnO nanorods increase both the open circuit voltage (V(OC)) and short circuit current density (J(SC)) relative to devices without CdS QDs. A photovoltaic device based that has been decorated with CdS QDs yields power conversion efficiency over 4 times greater than that for a similar device without CdS QDs. The best device yields a short circuit current density of 1.38 mAcm(-2) under AM1.5 illumination (100 MW cm(-2)), resulting in a power conversion efficiency of 0.21% The increase shows that the modification with CdS QDs can serve not only as a photosensitizer but mainly as an energy funnel and/or an electronic mediator to significantly improve the electron injection efficiency from P3HT to ZnO nanorods.
Improvement in photovoltaic performance for hybrid P3HT/elongated CdS nanocrystals solar cells with F-doped SnO(2) arrays
(2010-01-01)
Liao, Hung-Chou
;
Lin, Chin-Ching
;
Chen, Yu-Wei
;
Liu, Ta-Chung
;
Chen, San-Yuan
Hybrid CdS/P3HT photovoltaic devices using F-doped SnO(2) (FTO)-coated ZnO nanorod arrays as electrodes were studied in this work. The crystalline FTO, made using low-cost spray pyrolysis deposition (SPD), displayed a nominally complete and uniform coating over the entire outer surface of the ZnO nanorods. The photovoltaic performance of the CdS/P3HT photovoltaic devices increased with the FTO-coated ZnO nanorod length and thickness of the FTO layer, due to improvement in collecting photogenerated electrons, which results in the increased short circuit current density (J(SC)) and fill factor (FF) of the devices. The incorporation of CdS into the P3HT greatly enhanced the JSC of the devices with a nanorod FTO electrode. The power conversion efficiency (PCE) of the device with a ZnO nanorod length of 320 nm was increased from 0.37% for P3HT without CdS to 1.8% with CdS of AR = 1 (spherical shape). With a further increase of the AR of the CdS nanocrystal to 4, the PCE was further increased up to 2.6%. However, longer CdS nanocrystals conversely caused deterioration in PCE as a result of the nanorod array morphology. These results indicate that, although increased nanorod length could improve the photocurrent and efficiency, other factors, such as P3HT infiltration, nanorod array morphology and CdS nanocrystal length are required for obtaining the optimal performance of these devices.
Improvement in photovoltaic performance for hybrid P3HT/elongated CdS nanocrystals solar cells with F-doped SnO2 arrays
(2010-01-01)
Liao, Hung-Chou
;
Lin, Chin-Ching
;
Chen, Yu-Wei
;
Liu, Ta-Chung
;
Chen, San-Yuan
Hybrid CdS/P3HT photovoltaic devices using F-doped SnO2 (FTO)-coated ZnO nanorod arrays as electrodes were studied in this work. The crystalline FTO, made using low-cost spray pyrolysis deposition (SPD), displayed a nominally complete and uniform coating over the entire outer surface of the ZnO nanorods. The photovoltaic performance of the CdS/P3HT photovoltaic devices increased with the FTO-coated ZnO nanorod length and thickness of the FTO layer, due to improvement in collecting photogenerated electrons, which results in the increased short circuit current density (J(SC)) and fill factor (FF) of the devices. The incorporation of CdS into the P3HT greatly enhanced the JSC of the devices with a nanorod FTO electrode. The power conversion efficiency (PCE) of the device with a ZnO nanorod length of 320 nm was increased from 0.37% for P3HT without CdS to 1.8% with CdS of AR = 1 (spherical shape). With a further increase of the AR of the CdS nanocrystal to 4, the PCE was further increased up to 2.6%. However, longer CdS nanocrystals conversely caused deterioration in PCE as a result of the nanorod array morphology. These results indicate that, although increased nanorod length could improve the photocurrent and efficiency, other factors, such as P3HT infiltration, nanorod array morphology and CdS nanocrystal length are required for obtaining the optimal performance of these devices.
In-Situ Growing CdS Single-Crystal Nanorods via P3HT Polymer as a Soft Template, for Enhancing Photovoltaic Performance
(2009-09-08)
Liao, Hung-Chou
;
Chen, San-Yuan
;
Liu, Dean-Mo
;
材料科學與工程學系
;
Department of Materials Science and Engineering
A novel method was used to synthesize CdS single-crystal nanorods directly in the presence of conjugated polymer poly(3-hexylthiophene-2,5-diyl) (P3FIT), where the P3HT is acting as a molecular template for geometrical manipulation of CdS nanocrystals and, in the meantime, as in efficient charge conductor in composite form. Such a templating process allows the CdS nanorods with various aspect ratios to be easily manufactured via a controlled solvency of a cosolvent Mixture, under which the conformational variation of the P3HT chain can be manipulated. The mechanism of in situ growth of high-aspect-ratio CdS nanorod is proposed based on spectroscopic analysis. A considerably improved PL quenching was detected for the nanorods and suggested a result of electronic coupling between the high-aspect-ratio CdS nanorods and the conducting polymer matrix. A photovoltaic device consisting of CdS nanorods with aspect ratio of ea. 16 and the conjugated polymer poly(3-hexylthiophene) was well assembled and showed a power conversion efficiency of as high as 2.9% under air mass (AM) 1.5 global solar conditions.
Synthesis and optical properties of ZnO-ZnS core-shell nanotube arrays
(2006-09-01)
Liao, Hung-Chou
;
Kuo, Pai-Chia
;
Lin, Chin-Ching
;
Chen, San-Yuan
;
材料科學與工程學系
Heterostructured ZnO-ZnS core-shell nanotube arrays with the diameters of 50-80 nm and lengths up to I mu m were synthesized by a two-step chemical reaction. First, the ZnO layer was grown by atomic-layer deposition. It was found that the preferred, growth orientation was strongly dependent on the substrate temperature. After sulfuration conversion from arrayed ZnO nanorods, the ZnS-ZnO composite arrays can be successfully prepared, as evidenced from transmission electron microscopy. This confirms that the ZnO-ZnS core-shell nanotube-arrayed structure has been fabricated. X-ray photoelectron spectroscopy analysis indicates that the binding energy of S 2p is the same as that of bulk single-crystal ZnS and that the Zn 2p(3/2) peak is shifted about 0.5 eV due to the formation of Zn-S bonds. Photoluminescence shows the relative-intensity ratio of ultraviolet emission (I-UV) to deep-level emission (I-DLE) for ZnO/ZnS core-shell nanotubes can be enhanced to be nine times that of original ZnO nanotubes. (c) 2006 American Vacuum Society.