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ZnO:Al Doping Level and Hydrogen Growth Ambient Effects on CIGS Solar Cell Performance: Preprint
Cu(In,Ga)Se2 (CIGS) photovoltaic (PV) cells require a highly conducting and transparent electrode for optimum device performance. ZnO:Al films grown from targets containing 2.0 wt.% Al2O3 are commonly used for this purpose. Maximum carrier mobilities of these films grown at room temperature are ~20-25 cm2V-1s-1. Therefore, relatively high carrier concentrations are required to achieve the desired conductivity, which leads to free carrier absorption in the near infrared (IR). Lightly doped films (0.05 - 0.2 wt.% Al2O3), which show less IR absorption, reach mobility values greater than 50 cm2V-1s-1 when deposited in H2 partial pressure. We incorporate these lightly doped ZnO:Al layers into CIGS PV cells produced at the National Renewable Energy Laboratory (NREL). Preliminary results show quantum efficiency values of these cells rival those of a past world-record cell produced at NREL that used 2.0 wt.% Al-doped ZnO films. The highest cell efficiency obtained in this trial was 18.1%.
Date:
May 1, 2008
Creator:
Duenow, J. N.; Gessert, T. A.; Wood, D. M.; Egaas, B.; Noufi, R. & Coutts,T. J.
Object Type:
Article
System:
The UNT Digital Library
ZnTe:Cu Contact Optimization Strategies for Single-Junction and Multijunction CdS/CdTe PV Device Designs
The ability to produce high-performance CdS/CdTe photovoltaic (PV) devices that incorporate high-transparency back contacts for multijunction thin-film PV applications will require an even greater level of understanding than has been required for single-junction devices. This study reports some of our initial investigations at NREL to modify the ZnTe:Cu contact process previously developed for single-junction applications for optimal use as a transparent back contact. We have succeeded in producing devices incorporating a transparent ZnTe:Cu/ITO/metal-grid contact that demonstrates nominally identical light I-V (LIV) performance to the ZnTe:Cu/Ti contact used in single-junction devices. However, we have determined that the transparent conducting oxide (TCO), CdS, CdTe, and ZnTe:Cu layers are all factors in the optical absorption within the device. Finally, we have concluded that optimizing the transparent ZnTe:Cu contact for use with NREL-produced device material will require a more detailed understanding of the evolution of the junction region during the contact process.
Date:
May 1, 2003
Creator:
Gessert, T.; Coutts, T.; Dhere, R.; Duda, A. & Levi, D.
Object Type:
Article
System:
The UNT Digital Library
ZONE: a finite element mesh generator. [In FORTRAN IV for CDC 7600]
The ZONE computer program is a finite-element mesh generator which produces the nodes and element description of any two-dimensional geometry. The geometry is subdivided into a mesh of quadrilateral and triangular zones arranged sequentially in an ordered march through the geometry. The order of march can be chosen so that the minimum bandwidth is obtained. The node points are defined in terms of the x and y coordinates in a global rectangular coordinate system. The zones generated are quadrilaterals or triangles defined by four node points in a counterclockwise sequence. Node points defining the outside boundary are generated to describe pressure boundary conditions. The mesh that is generated can be used as input to any two-dimensional as well as any axisymmetrical structure program. The output from ZONE is essentially the input file to NAOS, HONDO, and other axisymmetric finite element programs. 14 figures. (RWR)
Date:
May 1, 1976
Creator:
Burger, M. J.
Object Type:
Report
System:
The UNT Digital Library
Zone Freezing Study for Pyrochemical Process Waste Minimization
Pyroprocessing technology is a non-aqueous separation process for treatment of used nuclear fuel. At the heart of pyroprocessing lies the electrorefiner, which electrochemically dissolves uranium from the used fuel at the anode and deposits it onto a cathode. During this operation, sodium, transuranics, and fission product chlorides accumulate in the electrolyte salt (LiCl-KCl). These contaminates change the characteristics of the salt overtime and as a result, large volumes of contaminated salt are being removed, reprocessed and stored as radioactive waste. To reduce the storage volumes and improve recycling process for cost minimization, a salt purification method called zone freezing has been proposed at Korea Atomic Energy Research Institute (KAERI). Zone freezing is melt crystallization process similar to the vertical Bridgeman method. In this process, the eutectic salt is slowly cooled axially from top to bottom. As solidification occurs, the fission products are rejected from the solid interface and forced into the liquid phase. The resulting product is a grown crystal with the bulk of the fission products near the bottom of the salt ingot, where they can be easily be sectioned and removed. Despite successful feasibility report from KAERI on this process, there were many unexplored parameters to help understanding …
Date:
May 1, 2012
Creator:
Williams, Ammon
Object Type:
Report
System:
The UNT Digital Library
Zone refining of plutonium metal
The purpose of this study was to investigate zone refining techniques for the purification of plutonium metal. The redistribution of 10 impurity elements from zone melting was examined. Four tantalum boats were loaded with plutonium impurity alloy, placed in a vacuum furnace, heated to 700{degrees}C, and held at temperature for one hour. Ten passes were made with each boat. Metallographic and chemical analyses performed on the plutonium rods showed that, after 10 passes, moderate movement of certain elements were achieved. Molten zone speeds of 1 or 2 inches per hour had no effect on impurity element movement. Likewise, the application of constant or variable power had no effect on impurity movement. The study implies that development of a zone refining process to purify plutonium is feasible. Development of a process will be hampered by two factors: (1) the effect on impurity element redistribution of the oxide layer formed on the exposed surface of the material is not understood, and (2) the tantalum container material is not inert in the presence of plutonium. Cold boat studies are planned, with higher temperature and vacuum levels, to determine the effect on these factors. 5 refs., 1 tab., 5 figs.
Date:
May 1, 1997
Creator:
unknown
Object Type:
Article
System:
The UNT Digital Library
ZPPR progress report: February 1988 through April 1988
Results are presented for control rod worth experiments in the axially heterogeneous assembly ZPPR-17, a part of the JUPITER-III program. From the earlier metal-fuel ZPPR-15 program, results are given for measurements and calculations of neutron spectra and sodium voiding in several configurations.
Date:
May 13, 1988
Creator:
Brumbach, S.B. & Collins, P.J.
Object Type:
Report
System:
The UNT Digital Library
THE ZrO$sub 2$-CaO-UO$sub 2$ CERAMIC FUEL FABRICATION FOR THE EBWR SPIKED CORE ELEMENTS. Final Report-Metallurgy Program 7.9.5
A series of experiments was proposed in which the thermal output of the EBWR is increased to 100 Mw. The increase in thermal enengy will be accomplished by inserting 32 spike elements in the initial fuel core. The fuel selected for the spike elements was a cubic solid solution in the system ZrO/sub 2/- CaO- UO/ sub 2/. The ceramic fuel was fabricated in the form of pellets by compacting a mixture of U/sub 3/O/sub 8/, CaCO/sub 3/, and ZrO/sub 2/. The pressed pellets were sintered in air at 1675 deg C plus or minus 25 deg C to form a cubic solid solution having a composition of 9.01 wt.% UO/sub 2/ (93% enriched), 9.07 wt.% CaO, and 81.92 wt.% ZrO/sub 2/. The procedures used in forming the fuel pellets are described. Following fabrication, the pellets were loosely inserted into Zircaloy-2 tubes for subsequent assembly into fuel elements. (auth)
Date:
May 1961
Creator:
Lied, R. C.; Lynch, E. D. & Handwerk, J. H.
Object Type:
Report
System:
The UNT Digital Library