Browsing by Author "Liu, Wen-Long"

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Engineering the bandgap of a two-dimensional photonic crystal with slender dielectric veins
(2007-10-01)
Liu, Wen-Long
;
Yang, Tzong-Jer
;
電子物理學系
;
Department of Electrophysics
This study proposes the double-hybrid-rods structure of two-dimensional (2D) photonic crystals of a square lattice. A square dielectric rod connected with slender rectangular dielectric veins on the middle of each side,of dielectric square rod. Some specific modes are found to be sensitive to certain structural parameters, such as the length, the dielectric constant and the shift of the position of the veins, etc., and giving rise to a new complete PBG at lower index bands. These results could be understood by the use of band structure point of view. In particular, by carefully adjusting the structural parameters, the band structure of the photonic crystal can be substantially engineered to achieve large bandgaps. (C) 2007 Elsevier B.V.. All rights reserved.
Photonic band gaps in a two-dimensional photonic crystal with open veins
(2006-10-01)
Liu, Wen-Long
;
Yang, Tzong-Jer
;
電子物理學系
;
Department of Electrophysics
We report two-dimensional (2D) photonic crystals of a square lattice with square dielectric rods growing slender veins on the middle side of each square dielectric rod in air. The complete photonic band gap (PBG) is found in higher index bands. Then extending the length of veins substantially shrinks this PBG, and for an appropriate vein length creates the new complete PBG at lower index bands. But the greatest complete PBG can be gotten where the veins are not fully closed at the lattice unit cell boundary. The photonic band gap is the result of considering the effects of Mie scattering due to the slender veins and interference of electromagnetic waves. Our results may provide a new direction for designing PBG of 2D photonic crystals. (c) 2006 Elsevier Ltd. All rights reserved.
Toward high efficiency and panel size 30 x 40 cm(2) Cu(I,Ga)Se-2 solar cell: Investigation of modified stacking sequences of metallic precursors and pre-annealing process without Se vapor at low temperature
(2014-11-01)
Wu, Tsung-Ta
;
Huang, Jyun-Hong
;
Hu, Fan
;
Chang, Chia-ho
;
Liu, Wen-Long
Modified stacking sequence of precursors and pre-annealing process on Se vapor at low temperature were applied to Cu(ln,Ga)Se-2 (CIGS) solar. The remarkable improvement of efficiency (5.53-10.10% and further 11.04%) and open circuit voltage (0.41 V-0.53 V and further 0.56 V) comes from a compact, smooth microstructure, and modified depth profile of Ga with suitable thickness of CuGa multi-stacking layers in the top of precursors as well as surface bandgap enhancement via pre-nnealing process without Se vapor followed by a specific non-toxic hydrogen-assisted solid Se vapor selenization process. The effects of microstructural, compositional and electrical characteristics of Ga distribution including accumulation and interdiffusion were examined in detail. Finally, a large-area (40 x 30 cm(2)) CIGS solar cell efficiency with improved open circuit voltage (V-OC) and fill factor (FE) of 36% and 14% has been demonstrated, yielding a promising efficiency of similar to 11.04%. (C) 2014 Elsevier Ltd. All rights reserved.