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5 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2002

CIGS2 Thin-Film Solar Cells on Flexible Foils for Space Power

CuIn(1-x)Ga(x)S2 (CIGS2) thin-film solar cells are of interest for space power applications because of the near optimum bandgap for AM0 solar radiation in space. CIGS2 thin film solar cells on flexible stainless steel (SS) may be able to increase the specific power by an order of magnitude from the current level of 65 Wkg(sup -1). CIGS solar cells are superior to the conventional silicon and gallium arsenide solar cells in the space radiation environment. This paper presents research efforts for the development of CIGS2 thin-film solar cells on 127 micrometers and 20 micrometers thick, bright-annealed flexible SS foil for space power. A large-area, dual-chamber, inline thin film deposition system has been fabricated. The system is expected to provide thickness uniformity of plus or minus 2% over the central 5" width and plus or minus 3% over the central 6" width. During the next phase, facilities for processing larger cells will be acquired for selenization and sulfurization of metallic precursors and for heterojunction CdS layer deposition both on large area. Small area CIGS2 thin film solar cells are being prepared routinely. Cu-rich Cu-Ga/In layers were sputter-deposited on unheated Mo-coated SS foils from CuGa (22%) and In targets. Well-adherent, large-grain Cu-rich CIGS2 films were obtained by sulfurization in a Ar: H2S 1:0.04 mixture and argon flow rate of 650 sccm, at the maximum temperature of 475 C for 60 minutes with intermediate 30 minutes annealing step at 120 C. Samples were annealed at 500 C for 10 minutes without H2S gas flow. The intermediate 30 minutes annealing step at 120 C was changed to 135 C. p-type CIGS2 thin films were obtained by etching the Cu-rich layer segregated at the surface using dilute KCN solution. Solar cells were completed by deposition of CdS heterojunction partner layer by chemical bath deposition, transparent-conducting ZnO/ZnO: Al window bilayer by RF sputtering, and vacuum deposition of Ni/Al contact fingers through metal mask. PV parameters of a CIGS2 solar cell on 127 micrometers thick SS flexible foil measured under AM 0 conditions at NASA GRC were: V(sub oc) = 802.9 mV, J(sub sc) = 25.07 mA per square centimeters, FF = 60.06%, and efficiency 0 = 8.84%. For this cell, AM 1.5 PV parameters measured at NREL were: V(sub oc) = 788 mV, J(sub sc) = 19.78 mA per square centimeter, FF = 59.44%, efficiency 0 = 9.26%. Quantum efficiency curve showed a sharp QE cutoff equivalent to CIGS2 bandgap of approximately 1.50 eV, fairly close to the optimum value for efficient AM0 PV conversion in the space.

Dhere, Neelkanth G.↗
DOE OSTI2020

Materials Data on Ga2Cu by Materials Project

CuGa2 crystallizes in the tetragonal P4/mmm space group. The structure is three-dimensional. Cu is bonded in a distorted body-centered cubic geometry to eight equivalent Ga atoms. All Cu–Ga bond lengths are 2.62 Å. Ga is bonded in a 9-coordinate geometry to four equivalent Cu and five equivalent Ga atoms. There are one shorter (2.54 Å) and four longer (2.84 Å) Ga–Ga bond lengths.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ga3Cu by Materials Project

CuGa3 is Uranium Silicide structured and crystallizes in the cubic Pm-3m space group. The structure is three-dimensional. Cu is bonded to twelve equivalent Ga atoms to form CuGa12 cuboctahedra that share corners with twelve equivalent CuGa12 cuboctahedra, edges with twenty-four equivalent GaGa8Cu4 cuboctahedra, faces with six equivalent CuGa12 cuboctahedra, and faces with twelve equivalent GaGa8Cu4 cuboctahedra. All Cu–Ga bond lengths are 2.85 Å. Ga is bonded to four equivalent Cu and eight equivalent Ga atoms to form GaGa8Cu4 cuboctahedra that share corners with twelve equivalent GaGa8Cu4 cuboctahedra, edges with eight equivalent CuGa12 cuboctahedra, edges with sixteen equivalent GaGa8Cu4 cuboctahedra, faces with four equivalent CuGa12 cuboctahedra, and faces with fourteen equivalent GaGa8Cu4 cuboctahedra. All Ga–Ga bond lengths are 2.85 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on GaCu3 by Materials Project

Cu3Ga is beta Cu3Ti-like structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. there are two inequivalent Cu sites. In the first Cu site, Cu is bonded to eight Cu and four equivalent Ga atoms to form CuGa4Cu8 cuboctahedra that share corners with four equivalent GaCu12 cuboctahedra, corners with fourteen equivalent CuGa4Cu8 cuboctahedra, edges with six equivalent GaCu12 cuboctahedra, edges with twelve CuGa4Cu8 cuboctahedra, faces with four equivalent GaCu12 cuboctahedra, and faces with sixteen CuGa4Cu8 cuboctahedra. There are six shorter (2.59 Å) and two longer (2.63 Å) Cu–Cu bond lengths. There are two shorter (2.60 Å) and two longer (2.61 Å) Cu–Ga bond lengths. In the second Cu site, Cu is bonded to eight equivalent Cu and four equivalent Ga atoms to form CuGa4Cu8 cuboctahedra that share corners with four equivalent GaCu12 cuboctahedra, corners with fourteen CuGa4Cu8 cuboctahedra, edges with six equivalent GaCu12 cuboctahedra, edges with twelve equivalent CuGa4Cu8 cuboctahedra, faces with four equivalent GaCu12 cuboctahedra, and faces with sixteen CuGa4Cu8 cuboctahedra. There are two shorter (2.60 Å) and two longer (2.61 Å) Cu–Ga bond lengths. Ga is bonded to twelve Cu atoms to form GaCu12 cuboctahedra that share corners with six equivalent GaCu12 cuboctahedra, corners with twelve CuGa4Cu8 cuboctahedra, edges with eighteen CuGa4Cu8 cuboctahedra, faces with eight equivalent GaCu12 cuboctahedra, and faces with twelve CuGa4Cu8 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on GaCu2 by Materials Project

Cu2Ga crystallizes in the orthorhombic Imma space group. The structure is three-dimensional. Cu is bonded in a 11-coordinate geometry to five equivalent Cu and six equivalent Ga atoms. There are a spread of Cu–Cu bond distances ranging from 2.42–2.62 Å. There are a spread of Cu–Ga bond distances ranging from 2.73–2.79 Å. Ga is bonded in a 12-coordinate geometry to twelve equivalent Cu and two equivalent Ga atoms. Both Ga–Ga bond lengths are 2.59 Å.

36 MATERIALS SCIENCE↗