Browsing by Author "Hsiao, Sheng-Wei"

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Depth-Profiling Electronic and Structural Properties of Cu(In,Ga)(S,Se)(2) Thin-Film Solar Cell
(2016-09-14)
Chiang, Ching-Yu
;
Hsiao, Sheng-Wei
;
Wu, Pin-Jiun
;
Yang, Chu-Shou
;
Chen, Chia-Hao
Utilizing a scanning photoelectron microscope (SPEM) and grazing-incidence X-ray powder diffraction (GIXRD), we studied the electronic band structure and the crystalline properties of the pentanary Cu(In,Ga)(S,Se)(2) (CIGSSe) thin-film solar cell as a function of sample depth on measuring the thickness-gradient sample. A novel approach is proposed for studying the depth-dependent information on thin films, which can provide a gradient thickness and a wide cross-section of the sample by polishing process. The results exhibit that the CIGSSe absorber layer possesses four distinct stoichiometries. The growth mechanism of this distinctive compositional: distribution formed by a two stage process is described according to the thermodynamic reaction and the manufacturing, process. On the basis of the depth-profiling results, the gradient profiles of the conduction and valence bands were constructed to elucidate the performance of the electrical properties (in this case, V-oc = 620 mV, J(sc) = 34.6 mA/cm(2), and eta = 14.04%); the valence-band maxima (VBM) measured with a SPEM in the spectroscopic mode coincide with this band-structure model, except for a lowering of the VBM observed in the surface region of the absorber layer due to the ordered defect compound (ODC). In addition, the depth-dependent texturing X-ray diffraction pattern presents the crystalline quality and the residual stress for each depth of a thin-film device. We find that the randomly oriented grains in the bottom region of the absorber layer and the different residual stress between the underlying Mo and the absorber interface, which can deteriorate the electrical performance due to peeling-off effect. An anion interstitial defect can be observed on comparing the anion concentration, of the elemental distribution with crystalline composition; a few excess sulfur atoms insert in interstitial sites at the front side of the absorber layer, whereas the interstitial selenium atoms insert at the back side.
Large Photoresponsivity in the Amorphous-TiO2/SrRuO(3)Heterostructure
(1970-01-01)
Liu, Heng-Jui
;
Huang, Chin-Han
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Chen, Cheng-Ying
;
Hsiao, Sheng-Wei
;
Chen, You-Sheng
Thin-film heterostructures are effective in enhancing the performance or triggering novel physical phenomena of optoelectronic applications. For example, the epitaxial heterostructures of ultraviolet-light-sensitive TiO(2)with metallic SrRuO(3)can acquire visible-light functionalities using the hot carrier injection mechanism. Therefore, the TiO2/SrRuO(3)heterostructure system has recently attracted increasing interest. Herein, the amorphous-TiO2/SrRuO(3)heterostructure is fabricated and compared to the epitaxial TiO2/SrRuO3. As opposed to the occurrence of the visible-light photovoltaic effect in the epitaxial TiO2/SrRuO3, the amorphous-TiO2/SrRuO(3)heterostructure herein exhibits different optoelectronic functionality, specifically the photoresistor behavior. The amorphous-TiO2/SrRuO(3)heterostructure achieves a photoresponsivity of 6.56 A W(-1)at 1 V. Such a performance is hardly obtained in typical oxide-based photoresistors. The analyses of the crystalline and electronic structures show that it is due to the defect-induced high electron doping in the amorphous TiO(2)with hot carrier injection mechanism. This study discusses the correlation between the hot carrier injection and band diagram, which provides more degrees of freedom in designing potential optoelectronic devices.