Browsing by Author "Hu, Weiguo"

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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.
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.
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.
Simulation study of type-II Ge/Si quantum dot for solar cell applications
(2013-09-28)
Hu, Weiguo
;
Rahman, Mohammad Maksudur
;
Lee, Ming-Yi
;
Li, Yiming
;
Samukawa, Seiji
The electronic structure, miniband formation conditions, and required process parameters of type-II Ge/Si quantum dots are calculated using a 3D finite element method. We further estimate the device conversion efficiency and optimize the appropriate operation conditions. By using the crystalline silicon as the matrix, the explored intermediate band solar cell (IBSC) may not be suitable for 1 sun application, but it is a great value under concentration application. By considering an appropriate H-passivation treatment on amorphous silicon, the type II Ge/Si IBSC can achieve 44.0% conversion efficiency under 1 sun application. (C) 2013 AIP Publishing LLC.
Type-II Ge/Si Quantum Dot superlattice for Intermediate-band Solar Cell Applications
(2013)
Hu, Weiguo
;
Fauzi, Mohd Erman
;
Igarashi, Makoto
;
Higo, Akio
;
Lee, Ming-Yi
A Ge/Si type-II quantum dot (QD) has been developed for use in all-Si intermediate-band solar cell (IBSC) applications. A top-down process is used to fabricate the ultra-high-quality QD superlattice. A newly developed 3D finite element method was used to solve several key design problems in achieving a practical structure. Theoretical calculations revealed that a heavy hole state can act as an ideal intermediate band when the interdot space ranges from 0.5 to 4 nm. An IBSC based on this superlattice dramatically enhanced conversion efficiency for concentration applications. For one-sun applications, H-passivizing Si and/or regrowthing amorphous SiC have a great potential to improve the conversion efficiency.