Research focus--The principal research effort of Dr. Compaan, on the
deposition of semiconductor thin films for solar cells, is supported by the
National Renewable Energy Laboratory (NREL).
Complete CdS/CdTe thin film solar cells are being fabricated at Toledo
with the CdS, CdTe, and CdCl2 deposited by pulsed laser deposition and radio frequency
(rf) planar magnetron sputtering. The
research emphasizes techniques scalable to large-area, thin-film modules for
applications of photovoltaic power generation.
Most of our research effort involves the use of glass substrates which are coated with
fluorine-doped tin oxide which serves as the transparent conductor. However, some research is directed to the
development of CdS/CdTe cells on flexible substrates such as molybdenum foil
and high temperature polymers. There
are currently two major projects supported by NREL. The first involves continuing research to improve the performance
of the CdTe-based cells and to study defects and non-uniformities in the thin
films which can lead to long term degradation of the cell performance. The second project involves
“next-generation” devices such as developing CdTe alloys suitable for a top
cell in a two-junction tandem configuration.
This to cell needs to have a band gap of about 1.7 eV compared with the
1.5 eV band gap of CdTe. We are also
working on the development of a transparent back contact (and/or “tunnel
junction”) for the top cell so that sunlight
(and current) can pass to the smaller-gap bottom cell.
Other faculty collaborate in this work. These include Profs. Victor Karpov, Randy Bohn, Xunming Deng in Physics and Astronomy, and Dean Giolando of the Chemistry Department.
Another related research effort of our group involves the development of improved thin films for flat-panel plasma display panel (PDP) technology and the study of vacuum-ultraviolet emission spectroscopy from PDP structures with time resolution of nanoseconds.
In
our labs we use a wide variety of characterization and diagnostic techniques
including Raman scattering, photoluminescence, x-ray diffraction, scanning electron
microscopy (SEM) with energy dispersive x-ray analysis (EDS), laser-induced
time-resolved fluorescence, photoreflectance and electroreflectance, spectral
quantum efficiency, and I-V device measurements. We collaborate with other research groups in using atomic force
microscopy (AFM), spectroscopic ellipsometry, Rutherford backscattering (RBS),
and synchrotron-based x-ray studies (grazing incidence x-ray fluorescence,
x-ray absorption near edge structure (XANES) and extended x-ray absorption fine
structure (EXAFS).
Recent
selected publications:
M. Shao, A. Fischer, D.
Grecu, U. Jayamaha, E. Bykov, G. Contreras-Puente, R.G. Bohn, and A.D. Compaan,
“Radio-frequency-magnetron-sputtered CdS/CdTe solar cells on soda-lime glass,”
Appl. Phys. Lett. 69, 3045-3047 (1996).
A. Fischer, L. Anthony and
A.D. Compaan, "Raman Analysis of Short-Range Clustering in Laser-Deposited
CdSxTe1-x Films," Appl. Phys. Lett. 72, 2559, (1998).
Y.L. Soo, S. Huang, Y.H.
Kao, and A.D. Compaan, "Investigation of interface morphology and
composition mixing in CdTe/CdS heterojunction photovoltaic materials using
synchrotron radiation," J. Appl. Phys. 83, 4173 (1998).
S. Huang, Y.L. Soo, Y.H.
Kao, and A.D. Compaan, "Annealing effects and Te mixing in CdTe/CdS
heterojunctions," Appl. Phys. Lett., 74,
218-220 (1999).
R. Wendt, A. Fischer, D.
Grecu and A.D. Compaan, "Improvement of CdTe solar cell performance with
discharge control during film deposition by magnetron sputtering," J.
Appl. Phys. 84, 2920-2925 (1998).
J.R. Gottschalk, A. Shvidky,
A.D. Compaan, C.E. Theodosiou, and W. Williamson, Jr., “Time-Resolved
Electrical and Optical Measurements in a Plasma Display Panel,” IEEE
Transactions on Plasma Science, 27,
772-777 (1999).
K. Wei, F.H. Pollak, J.L.
Freeouf, D. Shvydka, and A.D. Compaan, “Optical Properties of CdTe1-xSx
(0 £ x £ 1): Experiment and Modeling,” J. Appl. Phys. 85, 7418-7425 (1999).
D. Grecu and A.D. Compaan,
"Photoluminescence Study of Cu Diffusion and Electromigration in CdTe,
Appl. Phys. Lett. 75, 361-363 (1999).
A.D. Compaan, J.R. Sites, R.W. Birkmire, C.S.
Ferekides, and A.L. Fahrenbruch, "Critical Issues and Research Needs for
CdTe-Based Solar Cells," Photovoltaics for the 21st Century
Electrochemical Society Symposium
Proceedings, ECS99-11, edited by
V.J. Kapur, R.D. McConnell, D. Carlson, G.P. Ceasar,
and A. Rohatgi (1999) pp.241-251.
D. Grecu, A.D. Compaan, D. Young, U. Jayamaha, and
D.H. Rose, “Photoluminescence of Cu-doped CdTe and related stability issues in
CdS/CdTe solar cells,” J. Appl. Phys. 88,
2490 (2000).
Y.L. Soo, S. Huang, S. Kim, G. Kioseoglou, Y.H. Kao,
A.D. Compaan, D. Grecu, and D. Albin, “Effects of heat treatment on diffusion
of Cu atoms into CdTe single crystals,” Appl. Phys. Letts. 76, 3729 (2000).
A.D. Compaan, I Matulionis, and S. Nakade,
"Laser scribing of polycrystalline thin films," Optics and Lasers in
Engineering 34 15-45 (2000).
K. Makhratchev, K.J. Price, X. Ma, D.A. Simmons, J.
Drayton, K. Ludwig, A. Gupta, R.G. Bohn, & A.D. Compaan, "ZnTe:N Back
Contacts to CdS/CdTe Solar Cells," 28th IEEE Photovoltaic
Specialists Conference—2000, pp. 475-478 (IEEE, Piscataway, N.J.)
K.J. Price, D. Grecu, D. Shvydka, & A.D.
Compaan, "Photoluminescence of CdTe:Cu and CdS/Cu," 28th
IEEE Photovoltaic Specialists Conference—2000, pp. 658-661 (IEEE, Piscataway,
N.J.).
J. Drayton, A. Gupta, K. Makhratchev, K.J. Price,
R.G. Bohn, and A.D. Compaan, "Properties of RF Sputtered ZnTe:N for Back
Contact to CdS/CdTe Solar Cells," Mat. Res. Soc. Symp. Proc. 668, H5.9.1, 2001
Matulionis, S. Han, J.A. Drayton, K.J. Price, and
A.D. Compaan, "CdTe Solar Cells on Molybdenum Substrates," Mat. Res. Soc. Symp. Proc. 668, H8.23.1, 2001
D. Shvydka, A.D. Compaan, and K. J. Price,
"Absorption and photoluminescence studies of lightly alloyed CdTe(S) and
CdS(Te)," Mat. Res. Soc. Symp.
Proc. 668, H6.2.1, 2001
A. Gupta, I Matulionis, J. Drayton, and A.D.
Compaan, “Effect of CdTe thickness reduction in high efficiency CdS/CdTe solar
cells,” II-VI Compound Semiconductor
Photovoltaic Materials edited by R. Noufi, D. Lincot, and H.W. Schock [Mat.
Res. Soc. Symp. Proc. 668, H6.4.1,
(2001)].