Browsing by Author "Chiang, Mei-Ching"

Now showing 1 - 7 of 7

Effect of Oxygen on the Microstructural Growth and Physical Properties of Transparent Conducting Fluorine-Doped Tin Oxide Thin Films Fabricated by the Spray Pyrolysis Method
(2013)
Chantarat, N.
;
Chen, Yu-Wei
;
Hsu, Shu-Han
;
Lin, Chin-Ching
;
Chiang, Mei-Ching
We reported the fabrication of an FTO conducting thin film via a spray deposition method, which was used to investigate the effect of oxygen content in the carrier gas on deposited film morphology and properties. Using a carrier gas containing various O-2/N-2 concentrations (0%, 20%, 50%, 80%, and 100%) led to significant changes in the thickness, size, and shape of grain growth. The deposited films with 0-50% oxygen content yielded a low resistivity of similar to 10(-4) Omega-cm and a transmittance in the range of 76-96% at 550 nm. Furthermore, by changing the carrier gas concentration, the FTO films displayed different charge transport, recombination, and collection properties due to the surface and interfacial effects. These films with modified properties can be applied to dye-sensitized solar cells (DSSCs). Overall, the conversion efficiency of a solar cell based on a 0% O-2 sample was increased by approximately 2% from that of a 100% O-2 sample. The higher efficiency is mainly the result of the lower O-2 content, which minimized the grain boundaries (spacing) and improved the electron transport on the FTO film surface. (C) 2013 The Electrochemical Society. All rights reserved.
Mechanism of an AZO-coated FTO film in improving the hydrogen plasma durability of transparent conducting oxide thin films for amorphous-silicon based tandem solar cells
(2012)
Chantarat, N.
;
Hsu, Shu-Han
;
Lin, Chin-Ching
;
Chiang, Mei-Ching
;
Chen, San-Yuan
An Al-doped ZnO (AZO)/F-doped SnO2 (FTO) film structure in an amorphous silicon solar cell (a-Si: H) was studied under exposure to hydrogen (H) plasma treatment via a simple spray pyrolysis. A radio-frequency magnetron sputtering method was used to deposit the FTO film first and the subsequent AZO overlayer on top of the FTO. The results of this approach suggest that the AZO film acts as a protection layer for the underlying FTO film and thus provides an excellent interface that protects the film from the direct bombardment with H+ ions and radicals. Even under exposure to H-plasma, the optical (UV-Vis) and electrical properties (Hall measurement) of the AZO/FTO double layer film show improvement in plasma stability in comparison with a single FTO film. Without the AZO overlayer, the reduction of SnO2 to metallic Sn and sub-oxidized SnO can occur in the FTO film. However, after a post-annealing treatment at 400 degrees C, the degradation of the FTO can be reversed by reoxidizing the Sn-O bonds. This interpretation of the H+ ion diffusion and the Sn-O redox process is confirmed via XPS and SIMS analysis. This investigation provides an opportunity to study the H+ ion diffusion mechanism in a metal oxide matrix in the presence of plasma and thermal effects. The study thus provides an alternative to the conventionally used FTO-based Si solar cells.
Nitrogen Plasma-Assisted Codoped P-type (In, N):SnO(2) Ultra-Fine Thin Films and N-ZnO/p-In:SnO(2) Core-Shell Heterojunction Diodes Fabricated by an Ultrasonic Spray Pyrolysis Method
(2011-11-24)
Chantarat, N.
;
Chen, Yu-Wei
;
Lin, Chin-Ching
;
Chiang, Mei-Ching
;
Chen, Yu-Chun
In this study, tin oxide (SnO(2)) solution mixtures containing indium (In) of 0%, 3%, 7%, 15%, and 30% were used to fabricate In- and N-codoped SnO(2) films on glass at 400 degrees C using an ultrasonic spray pyrolysis method combined with thermal annealing at 600 degrees C and post nitrogen plasma treatment. X-ray diffraction analysis demonstrated that the incorporation of elemental In in the SnO(2) film primarily induces the evolution of crystalline phases from In-doped SnO(2) to Sn-doped In(2)O(3), depending on the doping concentration. Upon exposure to N plasma, the dark current dramatically increases in proportion to the treatment duration (5-40 min); the dark current can be enhanced for the 3% and 7%-doped samples by as much as 3 orders of magnitude compared to the untreated samples. Hall measurements confirmed that hole carriers could dominate the SnO(2) host matrix to promote p-type properties at a low In content (3% and 7%) with an increase in resistance compared to undoped samples. However, samples with higher In content (15% and 30%) showed the opposite trend, due to the formation of a secondary phase of n-type In(2)O(3). X-ray photoelectron spectroscopy was used to probe the incorporation and dissociation of chemical bonds between the doped In and N atoms in the SnO(2). Moreover, depth profile measurements showed a correlation between the elemental compositions and elemental distributions of the codoped SnO(2) film. Current-voltage (I-V) characterization revealed the improved behavior of heterojunction diodes consisting of a p-type (In, N)-doped SnO(2) thin film deposited on n-type ZnO nanorod arrays.
Nitrogen Plasma-Assisted Codoped P-type (In, N):SnO2 Ultra-Fine Thin Films and N-ZnO/p-In:SnO2 Core-Shell Heterojunction Diodes Fabricated by an Ultrasonic Spray Pyrolysis Method
(2011-11-24)
Chantarat, N.
;
Chen, Yu-Wei
;
Lin, Chin-Ching
;
Chiang, Mei-Ching
;
Chen, Yu-Chun
In this study, tin oxide (SnO2) solution mixtures containing indium (In) of 0%, 3%, 7%, 15%, and 30% were used to fabricate In- and N-codoped SnO2 films on glass at 400 degrees C using an ultrasonic spray pyrolysis method combined with thermal annealing at 600 degrees C and post nitrogen plasma treatment. X-ray diffraction analysis demonstrated that the incorporation of elemental In in the SnO2 film primarily induces the evolution of crystalline phases from In-doped SnO2 to Sn-doped In2O3, depending on the doping concentration. Upon exposure to N plasma, the dark current dramatically increases in proportion to the treatment duration (5-40 min); the dark current can be enhanced for the 3% and 7%-doped samples by as much as 3 orders of magnitude compared to the untreated samples. Hall measurements confirmed that hole carriers could dominate the SnO2 host matrix to promote p-type properties at a low In content (3% and 7%) with an increase in resistance compared to undoped samples. However, samples with higher In content (15% and 30%) showed the opposite trend, due to the formation of a secondary phase of n-type In2O3. X-ray photoelectron spectroscopy was used to probe the incorporation and dissociation of chemical bonds between the doped In and N atoms in the SnO2. Moreover, depth profile measurements showed a correlation between the elemental compositions and elemental distributions of the codoped SnO2 film. Current-voltage (I-V) characterization revealed the improved behavior of heterojunction diodes consisting of a p-type (In, N)-doped SnO2 thin film deposited on n-type ZnO nanorod arrays.
Photoconductive Enhancement of Single-Layer Tin Oxide-Coated ZnO Nanowires
(2010)
Lin, Chin-Ching
;
Chen, Yu-Wei
;
Chiang, Mei-Ching
;
Lee, Chia-Hua
;
Tung, Yung-Liang
In this study, zinc oxide nanowires (ZnO NWs) coated with crystalline tin oxide (SnO(2)) by an ultrasonic spray pyrolysis were investigated. High resolution transmission electron microscopy analysis confirms that a continuous single SnO(2) layer of about 10 nm has been coated on the ZnO NWs. Photoconductivity measurements revealed that the ZnO NWs coated with the single uniform SnO(2) layer had a higher photoconductivity ratio by about a factor of 8 compared to the pristine ZnO NWs, attributed to the multi-photoexcited electrons. Under a steady radiation of UV light (lambda=325 nm), a substantial increase in the steady-state photocurrent is noticeable, suggesting that extra photoinduced charges are transferred from SnO(2) to ZnO NWs.
Selective Oxygen-Plasma-Etching Technique for the Formation of ZnO-FTO Heterostructure Nanotubes and Their Rectified Photocatalytic Properties
(2010-12-06)
Chantarat, N.
;
Chen, Yu-Wei
;
Lin, Chin-Ching
;
Chiang, Mei-Ching
;
Chen, San-Yuan
A novel ZnO-FTO heterostructure nanotube array was produced by combining a chemical solution process with oxygen-plasma etching. In this approach, presynthesized ZnO nanorod arrays act as templates, and FTO nanoparticles are deposited onto the ZnO nanorods by a simple spray pyrolysis method. X-ray photoelectron spectroscopy analysis demonstrated that the oxygen-plasma treatment decreased the O(2-)/OH(-) concentration ratio, resulting in dissociation of the Zn-O bonds and the outward diffusion of Zn cations to form an interior hollow, which is related to the formation of the hydroxyl functional group, Sn-OH, at the FTO surface. An etching evolution mechanism of the ZnO-FTO nanotubes via oxygen plasma was tentatively proposed in this study. Time-dependent photocurrent (I-T) measurements under ON-OFF cycles of UV illumination confirm that the 20-min etched sample exhibits a rectified photoresponse characteristic and a dark current increased by about 3 orders of magnitude over that of the unetched sample, which is attributed to the increased carrier concentration created at the surface conductive layer. This investigation offers an alternative selective etching method to lay the framework for nanoscale three-dimensional electrodes for solar-cell applications.
Temperature dependence of Fluorine-doped tin oxide films produced by ultrasonic spray pyrolysis
(2009-12-15)
Lin, Chin-Ching
;
Chiang, Mei-Ching
;
Chen, Yu-Wei
;
材料科學與工程學系
;
Department of Materials Science and Engineering
Fluorine-doped tin oxide (FTO) films were prepared at different substrate temperatures by ultrasonic spray pyrolysis technique on glass substrates. Among F-doped tin oxide films, the lowest resistivitiy was found to be 6.2 x 10(-4) Omega-cm for a doping percentage of 50 mol% of fluorine in 0.5 M solution, deposited at 400 degrees C. Hall coefficient analyses and secondary ion mass spectrometry (SIMS) measured the electron carrier concentration that varies from 3.52 x 10(20) cm(-3) to 6.21 x 10(20) cm(-3) with increasing fluorine content from 4.6 x 10(20) cm(-3) to 7.2 x 10(20) cm(-3) in FTO films deposited on various temperatures. Deposition temperature on FTO films has been optimized for achieving a minimum resistivity and maximum optical transmittance. (C) 2009 Elsevier B.V. All rights reserved.