Photovoltaics
|
Photovoltaics
|
|
|
"If radiant energy production continues without limit, there remains hope that life capable of using it forever can be created" - Steven Frautschi, Science 217 (4560), 1982, p. 599
The Earth receives about 200,000 TeraWatts of optical power from the Sun on the exposed hemisphere at any given time. The planet's burgeoning population and rapid increase in per capita energy consumption requires a solution beyond fossil fuel. Our elected leaders aren't leading the charge on this front and don't appear to sense the impending and inevitable energy crunch! Photovoltaics (PV) offers us continuously renewable energy (right now) by direct conversion of sunlight into electricity. In America, PV is a 40+ year old interdisciplinary research field and has finally become a growth industry thanks to the perseverance of a few visionaries and supportively optimistic politicians and corporate investors. According to the Energy Information Administration of the U.S. Department of Energy, U.S. electric consumption is highest for heating and cooling, on the order of 0.3 GigaWatt Hours per day! To meet this demand solely with solar electric, I estimate that an array of solar modules with 10% conversion efficiency illuminated for 6 hours a day would require an area occupying 68 X 68 miles. My estimate of useful roof area on single family homes and apartments in the U.S.A. is about 53 X 53 miles. We ought to be deriving electricity from this abundant roof area! It seems clear that more efficient HVAC appliances coupled with widely distributed PV power can offset a large fraction of our energy demand. It means covering the roofs of our structures and creating large solar PV "farms". At this time (2008) it is happening in places like California and Delaware! (But in a small way compared to what is happening in Germany) Here is a picture of the Delaware home of my colleague, Steve Hegedus, whose meter runs backwards (!), with only a 1.8 kW polycrystalline silicon photovoltaic array, made by General Electric:
I joined the Institute of Energy Conversion at the University of Delaware in September of 1980. I was mentored by Bill Baron, Tony Catalano, Robert Birkmire, John Meakin, Rick Rocheleau and Fraser Russell in the fields of physical chemistry, applied physics, crystallography and chemical engineering. Now I develop thin-film solar cells using absorber layers comprised of chemical compounds such as Zn3P2, Cd3P2, FeS2, CdTe, ZnTe, CuInGaSe2. My present research focus is on increasing thin-film solar cell performance by raising open circuit voltage and voltage at maximum power. I am investigating the effects of widening the band gap, increasing doping and modifying properties which affect recombination in semiconductor films and structures made by low-cost, high-throughput processes suitable for manufacturing. This line of R&D requires making good baseline cells and state-of-art solar cells with each material system, understanding the action of individual processing steps on the baseline process by separating the effects of independent control variables, and then innovating with new processes and materials. Below are some photos and references to recent results in the polycrystalline group at IEC.
High throughput thin-film solar cell fabrication
Thin-film solar cells with vapor transport-deposited alloy absorber layers
Novel thin-film deposition and analysis
Recent Journal Publications
“Incongruent reaction of Cu-(Ga,In) intermetallic precursors in H2S and H2Se,” G. M. Hanket, B. E. McCandless, W. N. Shafarman, R. W. Birkmire, Journal of Applied Physics 102 (2007) 074922-1.
M. S. Angelo, B. E. McCandless, R. W. Birkmire, S. A. Rykov, J. G. Chen, "Contact wetting as a characterization technique for processing CdTe/CdS solar cells," Progress in Photovoltaics: Research and Applications 15 (2): 93-112 (2007).
G. M. Hanket, B. E. McCandless, W. A. Buchanan, S. Fields, and R. W. Birkmire, "Design of a vapor transport deposition process for thin film materials," Journal of Vacuum Science and Technology A 24(5) 1695-1701 (2006).
M. Estela Calixto, K. D. Dobson, B. E. McCandless and R. W. Birkmire, "Controlling growth chemistry and morphology of single-bath electrodeposited Cu(In,Ga)Se2 thin films for photovoltaic application," Journal of The electrochemical Society, 153(6) G521-528 (2006).
L. P. Shepherd, A. Mathew, B. E. McCandless, B. G. Willis, "Oxygen pressure dependence of copper ion transport in SiO2 dielectrics," Journal of Vacuum Science and Technology B 24(3) (2006).
S. S. Hegedus and B. E. McCandless, "CdTe contacts for CdTe/CdS solar cells: effect of Cu thickness, surface preparation and recontacting on device performance and stability," Solar Energy Materials and Solar Cells 88, 75-95 (2005)
B. E. McCandless and K. D. Dobson, "Processing options for CdTe thin film solar cells," Solar energy 77, 839-856 (2004).
P. D. Paulson, B. E. McCandless, R. W. Birkmire, "Optical properties of Cd1-xZnxTe films in a device structure using variable angle spectroscopic ellipsometry," Journal of Applied Physics 95(6) 3010-3019 (2004).
B. E. McCandless (Guest Editor), "Progress in Thin-film Solar Cells," Progress in Photovoltaics: Research and Applications 12 (2-3) (2004).
B. E. McCandless, S. S. Hegedus, R. W. Birkmire, D. Cunningham, "Correlation of surface phases with electrical behavior in thin film CdTe devices," Thin Solid Films 431-432, 249-256 (2003).
B. E. McCandless and J. R. Sites, "CdTe Solar Cells," Chapter 14 in Handbook of Photovoltaic Science and Engineering (A. Luque and S. Hegedus, Eds) Wiley 617-657 (2003).
B. E. McCandless, G. M .Hanket, D. G. Jensen, R. W. Birkmire, "Phase behavior in the CdTe-CdS pseudobinary system," Journal of Vacuum Science and Technology A 20(4) 1462-1467 (2002).
Links:
Institute of Energy Conversion: www.udel.edu/iec National Renewable Energy Lab: www.nrel.gov
Excellent Photovoltaics Educational Site: www.udel.edu/igert/pvcdrom
PV Dealer for Modules etc: www.backwoodssolar.com
|
|
Send mail to
bemccandless@earthlink.net with
questions or comments about this web site.
|
