Browsing by Author "Rahman, Mohammad Maksudur"

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Effect of ALD-Al2O3 Passivated Silicon Quantum Dot Superlattices on p/i/n(+) Solar Cells
(2017-07-01)
Rahman, Mohammad Maksudur
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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.
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
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Lee, Ming-Yi
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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.
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.
Simulation study of type-II Ge/Si quantum dot for solar cell applications
(2013-09-28)
Hu, Weiguo
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Rahman, Mohammad Maksudur
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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.