Xunming Deng (Materials Science)

Professor of Physics
Ph.D., 1990, University of Chicago

Dr. Deng's research interests are in the areas of amorphous silicon photovoltaic materials and devices, thin film depositions, and photo-electrochemical production of hydrogen.

Thin film amorphous silicon (a-Si) materials have been broadly used in photovoltaic devices, flat panel displays and different kinds of sensors. Amorphous silicon photovoltaic technology and products have shown promises for widespread applications due to low-cost processing, materials durability and environmentally friendliness. Dr. Deng is interested in a-Si related materials and devices and has established a strong research program at the University of Toledo to fabricate high-efficiency, multiple-junction, a-Si alloy solar cells. His research group has recently fabricated triple-junction a-Si solar cells with 12.5% active-area efficiency (11.8% total-area efficiency) as confirmed by National Renewable Energy Laboratory. This is the highest government-confirmed efficiency for a-Si based solar cells fabricated by an academic group. 

These triple-junction a-Si based solar cells that Dr. Deng's group fabricates are ideal as photoelectrodes for use in direct photo-electrochemical production of hydrogen from water under sunlight. This is because these solar cells have voltage sufficient to split water, can be easily deposited on conducting substrates, and are made using low-cost deposition fabrication process. 


Dr. Deng's group is currently developing a new hot-wire CVD process to deposit a-Si based materials at high deposition rate. Recent results suggest that a-Si films could be deposited using such a method at a growth rate up to 30 nm/s, which is two orders of magnitude higher than what is used in today's a-Si photovoltaic production. Such a high-rate deposition process, after fully developed, could potentially lead to significant cost reduction in a-Si manufacturing and photovoltaic products.


Some recent publications: 

·         X. Deng, X.B. Liao, S. Han, H. Povolny and P. Agarwal, "Amorphous silicon and silicon germanium materials for high efficiency triple-junction solar cells", Solar Energy Materials & Solar Cells, 62, 89 (2000).  [deng00a.pdf  574 kB]

·         G. Yue, X. Deng, G. Ganguly and D. Han,  "Electro- and Photo-Luminescence Spectra From a-Si and a-SiGe p-i-n Solar Cells",  J. of Non-Crystalline Solids, 266-269, 1119 (2000). 

·         H. Povolny, P. Agarwal, S. Han and X. Deng, “Comparison study of a-SiGe solar cells and materials deposited using different hydrogen dilution”, in Amorphous and Heterogenous Silicon Thin Films—2000, ed. by H. Branz, R. Collins, S. Guha, H. Okamoto and M. Stuztzmann, 2000.  [povolny00c.pdf  160 kB]

 ·        X. Deng, H. Povolny, S. Han and P. Agarwal,  “Ultra-lightweight amorphous silicon solar cells deposited on 7.5mm thick stainless steel substrates”, in Proceedings of 28th IEEE Photovoltaic Specialist Conf. (2000).  [deng00f.pdf  425 kB]

·         P. Agarwal, H. Povolny, S. Han and X. Deng, “Study of a-SiGe:H films and n-i-p devices used in high-efficiency triple-junction solar cells”, J. of Non-Cryst. Solids, 2001.  [agarwal01c.pdf  55 kB]

·         E.L. Miller, R.E. Rocheleau and X. Deng, “Design considerations for a hybrid amorphous silicon / photoelectrochemical multijunction cell for hydrogen production”, Proc. of International Symposium on Solar Hydrogen Fuel Cells- 2001, August 26-30, 2001, Cancun, Mexico. 

·         X. Deng, W. Wang, X. Liao, S. Han, H Povolny, X. Xiang, and W. Du, Proc. of NREL NCPV Program Review Meeting, 2001. [deng01a.pdf, 186kB] 

·         W. Wang, H. Povolny, W. Du, X.B. Liao and X. Deng, “Improved Triple-Junction a-Si Solar Cells with Heavily Doped Thin Interface Layers at the Tunnel Junctions”, to be published in Proc. of IEEE 29th Photovoltaic Specialist Conference, 2002. [wang02a.pdf, 189kB] 

·         X. Liao, H. Povolny, P. Agarwal and X. Deng,  “Raman and IR Study of Narrow Bandgap a-SiGe and mc-SiGe Films Deposited Using Different Hydrogen Dilution”, to be published in Proc. of IEEE 29th Photovoltaic Specialist Conference, 2002. [liao02a.pdf, 111kB] 

·         X.B. Liao, W. Wang and X. Deng, “AMPS Modeling of Nanocrystalline Si p-Layer in a-Si NIP Solar Cells”, to be published in Proc. of IEEE 29th Photovoltaic Specialist Conference, 2002. [liao02b.pdf, 55kB] 

·         X. Deng and E. Schiff, “Amorphous Silicon Related Solar Cells”, a chapter in Handbook of Photovoltaic Engineering, ed. A. Luque & S. Hegedus, to be published by John Wiley & Sons, Ltd. , 2002. 

E-mail: dengx@physics.utoledo.edu

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