Browsing by Author "Wu, P. W."

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Effect of Selenization Processes on CIGS Solar Cell Performance
(2018-07-01)
Wu, C. H.
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Wu, P. W.
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Chen, J. H.
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Kao, J. Y.
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Hsu, C. Y.
Cu(In, Ga)Se-2 (CIGS) films were fabricated by a two-step process method using sputtering from Cu0.7Ga0.3 and In targets. The metallic precursor structures of In/CuGa/In were prepared, and CuGa film was adjusted to the thicknesses of 150, 200, 250 and 300 nm, in order to optimize the CIGS film. After selenization, three independent CIGS (112), CIGS (220/204) and CIGS (312/116) began to crystallize at similar to 280 degrees C and phase peaks continued growing until 560 degrees C. Experimental results showed that with a single stage selenization method, the excessive stoichiometry of the CIGS films was obtained. Using three sequential stages for the selenization process, with a annealing time of 20 min, the stoichiometry of the CIGS absorbers with the Cu/(In + Ga) and Ga/(In + Ga) showed atomic ratios of 0.94 and 0.34, respectively. The intensity of the (112) XRD diffraction peak became stronger, indicating an improvement in the crystallinity. Raman spectra of CIGS absorbers showed a main peak (174 cm(-1)) and two weak signals (212 and 231 cm(-1)). TEM image for electron diffraction pattern showed that the grains were randomly oriented. CIGS solar cell device prepared with a proper selenization, a maximum efficiency of 12.45% was obtained.
Electrochemical Degradation of Nafion Ionomer to Functionalize Graphene As a Support for Core-Shell Palladium-Ruthenium Alloy @ Platinum Electrocatalysts
(2016-01-01)
Kuo, C. C.
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Chang, Y. C.
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Chou, C. L.
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Chou, S. C.
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Wu, P. W.
A simple but effective electrochemical route to functionalize graphene is demonstrated. Cyclic voltammetric sweeps are performed in H2SO4 aqueous solution on electrodes containing carbon cloth, graphene, and Nafion ionomer. With supply of ambient oxygen, the formation of hydroxyl radicals from the oxygen reduction reaction during CV cycles initiates the decomposition of Nafion ionomer that engenders oxygenated functional groups on the graphene surface. Raman analysis suggests a minor change for the graphene structure. Exploring various amounts of Nafion ionomer, we determine the optimized conditions for graphene functionalization. Contact angle is used to evaluate the effect of Nafion ionomer decomposition. X-ray photoelectron spectroscopy is employed to study relevant functional groups. Afterwards, nanoparticles of Pd9Ru are synthesized and impregnated on those functionalized graphene (FGN) via a wet chemical reflux process. X-ray diffraction patterns of the as-synthesized samples suggest successful formation of alloy. Images from transmission electron microscope confirm the average size of 3-4 nm. As expected, the Pd9Ru alloy are much more dispersive in FGN rather than in the one without functionalization.
The influences of surface treatment and gas annealing conditions on the inversion behaviors of the atomic-layer-deposition Al(2)O(3)/n-In(0.53)Ga(0.47)As metal-oxide-semiconductor capacitor
(2010-07-26)
Trinh, H. D.
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Chang, E. Y.
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Wu, P. W.
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Wong, Y. Y.
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Chang, C. T.
The inversion behaviors of atomic-layer-deposition Al(2)O(3)/n-In(0.53)Ga(0.47)As metal-oxide-semiconductor capacitors are studied by various surface treatments and postdeposition annealing using different gases. By using the combination of wet sulfide and dry trimethyl aluminum surface treatment along with pure hydrogen annealing, a strong inversion capacitance-voltage (C-V) response is observed, indicating a remarkable reduction in interface trap state density (D(it)) at lower half-part of In(0.53)Ga(0.47)As band gap. This low D(it) was confirmed by the temperature independent C-V stretch-out and horizontal C-V curves. The x-ray photoelectron spectroscopy spectra further confirm the effectiveness of hydrogen annealing on the reduction of native oxides. (C) 2010 American Institute of Physics. [doi:10.1063/1.3467813]
The influences of surface treatment and gas annealing conditions on the inversion behaviors of the atomic-layer-deposition Al2O3/n-In0.53Ga0.47As metal-oxide-semiconductor capacitor
(2010-07-26)
Trinh, H. D.
;
Chang, E. Y.
;
Wu, P. W.
;
Wong, Y. Y.
;
Chang, C. T.
The inversion behaviors of atomic-layer-deposition Al2O3/n-In0.53Ga0.47As metal-oxide-semiconductor capacitors are studied by various surface treatments and postdeposition annealing using different gases. By using the combination of wet sulfide and dry trimethyl aluminum surface treatment along with pure hydrogen annealing, a strong inversion capacitance-voltage (C-V) response is observed, indicating a remarkable reduction in interface trap state density (D-it) at lower half-part of In0.53Ga0.47As band gap. This low D-it was confirmed by the temperature independent C-V stretch-out and horizontal C-V curves. The x-ray photoelectron spectroscopy spectra further confirm the effectiveness of hydrogen annealing on the reduction of native oxides. (C) 2010 American Institute of Physics. [doi:10.1063/1.3467813]