Browsing by Author "Lee, Ming-Yi"

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50% Efficiency Intermediate Band Solar Cell Design Using Highly Periodical Silicon Nanodisk Array
(2012)
Hu, Weiguo
;
Igarashi, Makoto
;
Lee, Ming-Yi
;
Li, Yiming
;
Samukawa, Seiji
A high-quality Si nanodisk superlattice is fabricated by our top-down process. For the first time, a 3D finite element method (FEM) is developed to calculate energy band structure, optical and electrical properties, as well as the intermediate band solar cell (IBSC) operation for the realistic structure. Both the experiments and simulations reveal that miniband formation enhances the optical and electrical collections. Consequently, detailed electronic structure and conversion efficiency are examined to guide optimal design of minibands. A theoretically predicted maximal efficiency of the explored Si nanodisk superlattice is 50.3%, which is promising, compared with well-known complicated Si tandem solar cells.
Design and Simulation of Intermediate Band Solar Cell With Ultradense Type-II Multilayer Ge/Si Quantum Dot Superlattice
(2017-11-01)
Tsai, Yi-Chia
;
Lee, Ming-Yi
;
Li, Yiming
;
Samukawa, Seiji
;
資訊工程學系
We studied the miniband dependence on the structural parameters and shape in type-II multilayer germanium (Ge)/silicon (Si) quantum dot superlattice (QDSL) solar cell. A maximum tunable range of ground-state energy is 19% by tuning layer distance down to 0.5 nm, whereas 24.5% is achieved by adjusting the horizontal dot-to-dot spacing down to 0.3 nm. The reduction of effective bandgap is severe for cylindrical QDs than ellipsoidal and conical QDs in the ultradense QDSL, thus leading to a relatively lower conversion efficiency. On average, the thickness of QD shows a negative correlation to conversion efficiency. We observed a high conversion efficiency of 27.22% in a bilayer conical QDSL under an AM1.5 spectral irradiance and one sun illumination.
Design and Simulation of Si/SiC Quantum Dot Superlattice Solar Cells with Al2O3 Passivation Layer
(2017-01-01)
Tsai, Yi-Chia
;
Lee, Ming-Yi
;
Li, Yiming
;
Samukawa, Seiji
;
電信工程研究所
By simultaneously considering the enhancement of quantum confinement on the effective bandgap and minimum transition energy, the silicon (Si)! silicon carbide (SiC) quantum dot superlattice (SiC-QDSL) with aluminum oxide (A1203-QDSL) passivation layer shows the high short-circuit current (J,) of 4.77 mA/cm(2) in theoretical, which agrees with the J, of 4.75 mA/cm(2) obtained in the experiment under an AM1.5 and one sun illumination. Moreover, the reduction of efficiency in an ultra-dense QD configuration can be ameliorated by exploiting the Al2O3 passivation layer. As the result, a high conversion efficiency of 16.3% is optimized by using the QD geometry from experiment and an inter-dot spacing of 0.3 nm.
Effect of ALD-Al2O3 Passivated Silicon Quantum Dot Superlattices on p/i/n(+) Solar Cells
(2017-07-01)
Rahman, Mohammad Maksudur
;
Tsai, Yi-Chia
;
Lee, Ming-Yi
;
Higo, Akio
;
Li, Yiming
The photovoltaic (PV) nature of the silicon (Si) quantum dot super lattice (QDSL) is studied with an atomic-layer-deposited aluminum oxide film (ALD-Al2O3) and a conventional sputtered-grown amorphous silicon carbide film (a-SiC). The QDSL structures act as an intermediate layer in a p/i/n(+) Si solar cell. The QDSL consists of 4-nm Si on 2-nm SiC nanodisks (NDs) arrayed in an ALD-Al2O3 and a-SiC passivation matrix. Formation of Si-NDs was confirmed by bright field scanning transmission electron microscope. A significant PV response in generating a high photocurrent density J(sc) of 30.15mA/cm(2), open circuit voltage V-oc of 0.50 V, fill factor FF of 0.61, and efficiency. of 9.12% was observed in ALD-Al2O3/QDSL solar cell with respect to a-SiC/QDSL solar cell with J(sc) of 26.94 mA/cm(2), V-oc of 0.50 V, FF of 0.47, and eta of 6.42%. A wide range of photo-carrier transports by the ALD-Al2O3/QDSL structure is possible in the external quantum efficiency spectra with respect to a-SiC/QDSL solar cell. The enhanced PV performance of the QD solar cells was clarified in terms of simulating the absorption contributions for all possible transitions in the nanostructure with different passivation films.
Electronic Structure Dependence on the Density, Size and Shape of Ge/Si Quantum Dots Array
(2015)
Lee, Ming-Yi
;
Tsai, Yi-Chia
;
Li, Yiming
;
Samukawat, Seiji
;
電信工程研究所
In this work, an efficient method is proposed to calculate the miniband structure and density of states for well-ordered Ge/Si-nanodisk array. Within the envelop-function framework, our approach surmounts theoretical approximations of the multi-dimensional Kronig-Penney method and provides a guideline for three-dimensional quantum dots design by simulating the effect of the interdot space on miniband structure.
Impact of silicon quantum dot super lattice and quantum well structure as intermediate layer on p-i-n silicon solar cells
(2016-06)
Rahman, Mohammad Maksudur
;
Lee, Ming-Yi
;
Tsai, Yi-Chia
;
Higo, Akio
;
Sekhar, Halubai
The photovoltaic effect of the silicon (Si)/silicon carbide (SiC) quantum dot super lattice (QDSL) and multi-quantum well (QW) strucutres is presented based on numerical simulation and experimental studies. The QDSL and QW structures act as an intermediate layer in a p-i-n Si solar cell. The QDSL consists of a stack of four 4-nm Si nano disks and 2-nm SiC barrier layers embedded in a SiC matrix fabricated with a top-down etching process. The Si nano disks were observed with bright field-scanning transmission electron microscopy. The simulation results based on the 3D finite element method confirmed that the quantum effect on the band structure for the QDSL and QW structures was different and had different effects on solar cell operation. The effect of vertical wave-function coupling to form a miniband in the QDSL was observed based on the solar-cell performance, showing a dramatic photovoltaic response in generating a high photocurrent density J(sc) of 29.24mA/cm(2), open circuit voltage V-oc of 0.51V, fill factor FF of 0.74, and efficiency eta of 11.07% with respect to a i-QW solar cell with J(sc) of 25.27mA/cm(2), V-oc of 0.49V, FF of 0.69, and eta of 8.61% and an i-Si solar cell with J(sc) of 27.63mA/cm(2), V-oc of 0.55V, FF of 0.61, and eta of 10.00%. A wide range of photo-carrier transports by the QD arrays in the QDSL solar cell is possible in the internal quantum efficiency spectra with respect to the internal quantum efficiency of the i-QW solar cell. Copyright (C) 2015 John Wiley & Sons, Ltd.
Innovation of Digitalized Microfluidic System with Electrowetting-on-Dielectric (EWOD) Chip Used in In Vitro Embryo Culture System.
(2012-03-01)
Huang, Hong-Yuan
;
Yao, Da-Jeng
;
Huang, Hung-Ju
;
Fan, Shih-Kang
;
Li, Chin-Jung
Miniband Calculation of 3-D Nanostructure Array for Solar Cell Applications
(2015-11-01)
Lee, Ming-Yi
;
Li, Yiming
;
Samukawa, Seiji
;
電信工程研究所
;
Institute of Communications Engineering
Within the envelop-function framework, we propose a more efficient finite-element method to calculate the miniband structure and density of states in an idealistic nanocrystal array with realistic geometrical parameters. This method clearly reveals the miniband formation and accurately calculates the energy dispersion relationship. The calculated result agrees well with the analytical Kronig-Penney method. More importantly, this method surmounts the theoretical approximations of the multidimensional Kronig-Penney method, and provides significant information for 3-D quantum dots solar cell design by simulating an in-plane germanium nanodisk array in bulk silicon.
Miniband formulation in Ge/Si quantum dot array
(2016-04)
Tsai, Yi-Chia
;
Lee, Ming-Yi
;
Li, Yiming
;
Samukawa, Seiji
;
電信工程研究所
In this work, we estimate the coupling effect of miniband structure and density of states (DoS) resulting from different qunatum-dot physical parameters in a well-aligned Ge/Si quantum dot (QD) array fabricated by neutral beam etching technology. The density of QDs dominates the coupling effect and miniband\'s bandwidth, the radius of QDs affects the magnitude of energy levels and miniband bandwidth, and the thickness of QDs has a great impact on the magnitude of energy levels. Among the different shapes of Ge/Si QDs, discoid QDs exhibit the most band crossing and broadest bandwith under the same physical parameters. (C) 2016 The Japan Society of Applied Physics
Miniband formulation in Ge/Si quantum dot array
(2016-04-01)
Tsai, Yi-Chia
;
Lee, Ming-Yi
;
Li, Yiming
;
Samukawa, Seiji
;
電信工程研究所
In this work, we estimate the coupling effect of miniband structure and density of states (DoS) resulting from different qunatum-dot physical parameters in a well-aligned Ge/Si quantum dot (QD) array fabricated by neutral beam etching technology. The density of QDs dominates the coupling effect and miniband's bandwidth, the radius of QDs affects the magnitude of energy levels and miniband bandwidth, and the thickness of QDs has a great impact on the magnitude of energy levels. Among the different shapes of Ge/Si QDs, discoid QDs exhibit the most band crossing and broadest bandwith under the same physical parameters. (C) 2016 The Japan Society of Applied Physics
Miniband Formulation of Bilayer Type II Ge/Si Quantum Dot Superlattices
(2016)
Tsai, Yi-Chia
;
Lee, Ming-Yi
;
Li, Yiming
;
Samukawa, Seiji
;
電信工程研究所
This article presents a computational study on the impact of layer distance on the miniband formulation and density of state under different quantum dot structural parameters-height, interdot space-in a bilayer and well-aligned Ge/Si quantum-dot array. The miniband bandwidth, energy and effective bandgap is tunable by introducing an additional quantum dot layer. When the vertical distance between layers is smaller than 2.0 nm, the individual band structure of each layer will separate and couple into a broader bandwidth. The effective bandgap decreases since the highest excited states, with broader bandwidth, mix with and become continuous energy levels.
Modeling and Simulation of Ge/Si-Nanodisk Array for QD-based IB Solar Cells
(2016-01-01)
Lee, Ming-Yi
;
Tsai, Yi-Chia
;
Li, Yiming
;
Samukawa, Seiji
;
電信工程研究所
A computationally efficient finite element simulation is performed to calculate the miniband structure and DoSs for the well-ordered Ge/Si-nanodisk array. The semiconductor nanostructures are fabricated by using self-assemble bio-template and damage-free NBE technique. Within the envelop-function framework, our model surmounts theoretical approximations of the multidimensional Kronig-Penney method and accurately calculates the energy dispersion relationship. The miniband formation works as the intermediate band within the bandgap of bulk silicon band. Effects of the interdot space, the radius and thickness of the Ge/Si-nanodisk on the miniband structure, and conversion efficiency of the solar cell (SC) are discussed. The findings of this study provide a guideline for 3D QDs IBSC design.
Modeling miniband for realistic silicon nanocrystal array
(2013-07-01)
Hu, Weiguo
;
Budiman, Mohd Fairuz
;
Igarashi, Makoto
;
Lee, Ming-Yi
;
Li, Yiming
Within the envelop-function framework, we developed the finite element method to calculate the minibands in the realist Silicon nanocrystal array. This method clearly reveals the miniband formation and accurately calculates the E-K dispersion relationship. In the simple 1D array, the deduced miniband structure matches well with the analytic Kronig-Penney method. More importantly, it can better simulate the 2D and 3D nanocrystal array, which avoids approximations of the quantum cubic box and the independent periodic potential of the multi-dimension Kronig-Penney method. Further, this model is utilized to calculate miniband structure of realistic 2D-array Silicon nanodisk array for guiding quantum dot solar cell design. (C) 2012 Elsevier Ltd. All rights reserved.
Numerical Simulation of Highly Periodical Ge/Si Quantum Dot Array for Intermediate-Band Solar Cell Applications
(2015)
Tsai, Yi-Chia
;
Lee, Ming-Yi
;
Li, Yiming
;
Samukawa, Seiji
;
電信工程研究所
In this work, an efficient method is applied to calculate the miniband structure and density of states for well-ordered Ge/Si quantum dot (QD) array fabricated by combining the self-assemble bio-template and damage-free neutral beam etching. Within the envelop-function framework, this computational model surmounts theoretical approximations of the multidimensional Kronig-Penney method and the numerical results provide a guideline for Ge/Si QD solar cell design by simulating the effect of the interdot space and QD\'s dimension on miniband structure and conversion efficiency.
Numerical Simulation of Physical and Electrical Characteristics of Ge/Si Quantum Dots Based Intermediate Band Solar Cell
(2016)
Lee, Ming-Yi
;
Tsai, Yi-Chia
;
Li, Yiming
;
Samukawa, Seiji
;
電信工程研究所
According to the Bloch theorem and the symmetry of superlattice configuration, a new 3D finite element method is employed to calculate the miniband structure and density of state for well-aligned Ge/Si QDs array. This method can overcome the approximation of multi-dimensional Kronig-Penny model and constrain on QDs superlattice structure. The interaction of electronic structure among Ge/Si QDs with various density of QDs therough QDs dimension and superlattice structure is investigated to provide a design guideline for QDs solar cell.
Numerical Simulation of Thermal Conductivity of SiNW-SiGe0.3 Composite for Thermoelectric Applications
(2020-05-01)
Lee, Ming-Yi
;
Li, Yiming
;
Chuang, Min-Hui
;
Ohori, Daisuke
;
Samukawa, Seiji
The electron band structure and phonon energy dispersion of the silicon nanowires (SiNWs) embedded in SiGe0.3 (SiNW-SiGe0.3 composite) are simulated by using the effective mass Schrodinger equation and the elastodynamic wave equation, respectively. Then, the TE properties of the SiNW-SiGe0.3 composite are investigated by the Landauer approach. The simulation shows the contribution from electrons/holes on both electrical conductance and thermal conductance increases few times by introducing SiNWs, but on the other hand, lattice thermal conductance reduces around two orders. These results are consistent with the experimental measurement and indicates that much lower lattice thermal conductance dominates the TE performance of the SiNW-SiGe0.3 composite.
Realistic quantum design of silicon quantum dot intermediate band solar cells
(2013-07-05)
Hu, Weiguo
;
Igarashi, Makoto
;
Lee, Ming-Yi
;
Li, Yiming
;
Samukawa, Seiji
A highly periodical Si nanodisk superlattice has been fabricated by our top-down process. Based on the realistic structure, a 3D simulation program using the finite element method is developed to calculate energy band structure, optical and electrical properties, as well as the intermediate band solar cell operation. Both the experiments and simulations reveal that miniband formation enhances the optical and electrical collections. Consequently, detailed electronic structure and conversion efficiency are examined to guide the optimal design of minibands. A theoretically predicted maximal efficiency of the explored Si nanodisk superlattice is 50.3%, which is promising, compared with well-known complicated Si tandem solar cells.
Removal of pharmaceuticals and organic matter from municipal wastewater using two-stage anaerobic fluidized membrane bioreactor
(2014-08-01)
Dutta, Kasturi
;
Lee, Ming-Yi
;
Lai, Webber Wei-Po
;
Lee, Chien Hsien
;
Lin, Angela Yu-Chen
The aim of present study was to treat municipal wastewater in two-stage anaerobic fluidized membrane bioreactor (AFMBR) (anaerobic fluidized bed reactor (AFBR) followed by AFMBR) using granular activated carbon (GAC) as carrier medium in both stages. Approximately 95% COD removal efficiency could be obtained when the two-stage AFMBR was operated at total HRT of 5 h (2 h for AFBR and 3 h for AFMBR) and influent COD concentration of 250 mg/L. About 67% COD and 99% TSS removal efficiency could be achieved by the system treating the effluent from primary clarifier of municipal wastewater treatment plant, at HRT of 1.28 h and OLR of 5.65 kg COD/m(3) d. The system could also effectively remove twenty detected pharmaceuticals in raw wastewaters with removal efficiency in the range of 86-100% except for diclofenac (78%). No other membrane fouling control was required except scouring effect of GAC for flux of 16 LMH. (C) 2014 Elsevier Ltd. All rights reserved.
Removal of pharmaceuticals and organic matter from municipal wastewater using two-stage anaerobic fluidized membrane bioreactor
(2014-08-01)
Dutta, Kasturi
;
Lee, Ming-Yi
;
Lai, Webber Wei-Po
;
Lee, Chien Hsien
;
Lin, Angela Yu-Chen
The aim of present study was to treat municipal wastewater in two-stage anaerobic fluidized membrane bioreactor (AFMBR) (anaerobic fluidized bed reactor (AFBR) followed by AFMBR) using granular activated carbon (GAC) as carrier medium in both stages. Approximately 95% COD removal efficiency could be obtained when the two-stage AFMBR was operated at total HRT of 5 h (2 h for AFBR and 3 h for AFMBR) and influent COD concentration of 250 mg/L. About 67% COD and 99% TSS removal efficiency could be achieved by the system treating the effluent from primary clarifier of municipal wastewater treatment plant, at HRT of 1.28 h and OLR of 5.65 kg COD/m(3) d. The system could also effectively remove twenty detected pharmaceuticals in raw wastewaters with removal efficiency in the range of 86-100% except for diclofenac (78%). No other membrane fouling control was required except scouring effect of GAC for flux of 16 LMH. (C) 2014 Elsevier Ltd. All rights reserved.
Simulation Study of Multilayer Si/SiC Quantum Dot Superlattice for Solar Cell Applications
(2016-06)
Tsai, Yi-Chia
;
Lee, Ming-Yi
;
Li, Yiming
;
Rahman, Mohammad Maksudur
;
Samukawa, Seiji
This letter presents a computational study on the band profile of Si/SiC quantum dot (QD) superlattice for solar cell devices and the theoretical conversion efficiency. We find that both the miniband energy of QD superlattice and the conversion efficiency of QD solar cell highly correlate to the space among layers and the number of layers. When the distance between layers is >2 nm, the impact of the number of layers on the tunable ground-state energy bandwidth is weakened. The conversion efficiency increases as the layer distance decreases; however, when the number of layers is greater than 4, the increasing rate of conversion efficiency declines.