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2004 World Technology Awards Winners & Finalists

Ting Chu

Please describe the work that you are doing that you consider to be the most innovative and of the greatest likely long-term significance.

TING L. CHU - IMPORTANT CONTRIBUTIONS

The use of photovoltaic solar energy conversion for terrestrial power generation has been a major objective of the National Renewable Energy Program since the early seventies. While single crystalline silicon, and recently gallium arsenide, solar cells have been used successfully and extensively for various space applications, their cost must be drastically reduced for terrestrial applications. The fabrication of single crystalline silicon and gallium arsenide solar cells requires expensive materials and numerous processing steps. Thus, the material and processing costs must be reduced. The use of thin film solar cells has great potential to fulfill the cost requirements if reasonable conversion efficiency can be achieved.

Ting L. Chu participated in the research and development of thin film solar cells from 1973 until his retirement in 1995. At the Workshop on Photovoltaic Conversion of solar Energy for Terrestrial Applications sponsored by the National Science Foundation in October 1973, he chaired the Working Group on Polycrystalline Silicon Solar Cells and and formulated the National Program in this area. In 1976, he conducted the National Workshop on Low Cost Polycrystalline Silicon Solar Cells sponsored by the National Science Foundation. The results of that Workshop stimulated research and development in many sectiors of the photovoltaic community.

With experience in semiconductor materials and devices, he and his group carried out extensive investigations on (1) the preparation and characterization of thin films (mostly polycrystalline) of many potentially useful semiconductors and (2) the fabrication and evaluation of thin film solar cells from these semiconductor films. The materials studied included crystalline silicon, amorphous silicon, gallium arsenic, indium phosphide, cadmium telluride, zinc telluride, copper indium diselenide, and copper indium disulfide. Except silicon, other materials are direct-gap semiconductors with high optical absorption coefficients for above-gap radiation. The important contributions are:

(1) He pioneered the research on thin film silicon solar cells including the development of silicon film deposition techniques, and the correlation of material properties (grain size and grain boundaries, minority carrier diffusion length, impurity content, and etc.) with solar cell performance and staility, contributing to the understanding of grain boundaries in silicon films. His work has influened several industrial organizations (RCA and Honeywell, for example) in their research on low cost silicon solar cells. He was the first to demonstrate large area thin film silicon solar cell with a near 10% efficiency in 1978. He received several certificates of recognition from the National Aeronautics and Space Administration.

(2) He was the first to report on the fabrication of thim film cadmium telluride solar cells with 14.6% efficiency in 1991 by several innovative processes. Different from thin film silicon solar cells, cadmium telluride solar cell is a heterojunction structure consisting of the successive deposition of fluorine-doped tin-oxide (0.4-0.6 ?m), cadmium sulfide (0.05-0.08 ?m), p-type cadmium telluride (2-4 ?m), and ohmic contact on glass substrates. Various cadmium telluride deposition techniques were evaluated with respect to control of carrier concentration, grain size, and reproducibility. A new low-resistance ohmic contact material to p-cadmium telluride was developed. The deposition of cadmium sulfide and tin oxide was optimized with respect to their optical property and electrical conductivity. The relative high efficiency of laboratory solar cells provides an incentive for further development for terrestrial power generation. The characteristics of thim film cadmium telluride solar cells have been gradually improved during the past ten years.

(3) He developed for the first time the deposition of hydrogenated amorphous silicon (?-Si) films at high rate (1?m/min) with electronic properties (minority carrier diffusion length, gap state density, etc.) similar to those of good quality ?-Si films prepared by glow discharge. Further, these films are significantly more stable under illumination than glow-discharge films.

(4) He developed novel techniques for the low-cost deposition of large area cadmium sulfide and copper indium diselenide films.

(5) He has trained more than forty post-doctoral associates and about twenty Ph.D. students in phorovoltaics. They all enjoy respectable positions in academic or industrial organizations.

Brief Biography

TING L. CHU - BIOGRAPHY

12 Duncannon Court, Dallas, TX 75225-1809 Phone: (214) 368-2046; FAX: (214) 368-2536; e-mail: tishchu@aol.com

DATE AND PLACE OF BIRTH: December 26, 1924, Peking, China (naturalized November 16, 1961)

EDUCATION: Catholic University of Peking, China, B.S., 1945; M.S., 1948 Washington University, St. Louis, Missouri, Ph.D., 1952

EXPERIENCE:

Duquesne University: 1952-56, Assistant Professor, Associate Professor Westinghouse Research Laboratories: 1956-67, Research Scientist, Fellow Scientist, Manager of Epitaxial Growth and Electronic Materials Southern Methodist University: 1967-88: Professor of Electronic Sciences and Electrical Engineering, 1971-73, Acting Director, Electronic Sciences Center University of South Florida: 1988-91, Graduate Research Professor of Electrical Engineering 1992- Graduate Research Professor Emeritus of Electrical Engineering Consultancy: Westinghouse Research Laboratories 1967-69 Texas Instruments Incorporated, 1969-1975 Monsanto, NCR, Union Carbide, 1975-77 Poly Solar Incorporated, 1978-88 Solar Cells, Inc., 1991-1992 National Renewable Energy Laboratory, 1992-94 Golden Photon, Inc., 1992-95

RESEARCH INTERESTS:

Thin Film Devices for Photovoltaic solar energy conversion Crystal growth and preparation of electronic materials from the melt, the solution, and the vapor phase Device processing technology including epitaxial growth, diffusion, oxidation, contacting, and passivation Structural and electrical characterization of electronic materials, dielectric-semiconductor structures, and Junction devices

PROFESSIONAL SOCIETIES MEMBERSHIPS:

Electrochemical Society Institute of Electrical and Electronics Engineers

HONORS AND AWARDS:

Outstanding Educator of America, 1972; Outstanding Professor for 1973, Southern Methodist University Five Certificates of Recognition from the National Aeronautics and Space Administration Seventeen Patents

PUBLICATIONS - BOOKS:

"Proceedings of the National Workshop on Low Cost Polycrystalline Silicon Solar Cells," (with Shirley S. Chu), May, 1986, 468 pp, Dallas, Texas. "Growth of Epitaxial Films for VLSI Applications," Chapter 17 in VLSI Handbook, pp. 285-304, Academic Press, 1985. "Cadmium Telluride Solar Cells," Chapter 3 in Current Topics in Photovoltaics, pp. 235-300, Academic Press, 1988. "Cadmium Telluride Photovoltaics," (with K. Zweibel and S. S. Chu), Chapter 16 in Advances in Solar Energy, Vol.8, pp. 271-343, American Solar Energy Society, Inc., 1993.