Highly Transparent Compositionally Graded Buffers for New Metamorphic Multijunction Solar Cell Designs

Journal Article · Fri Nov 11 00:00:00 EST 2016 · IEEE Journal of Photovoltaics

DOI:https://doi.org/10.1109/JPHOTOV.2016.2619183· OSTI ID:1342505

Schulte, Kevin L. ^[1]; France, Ryan M. ^[1]; Geisz, John F. ^[1]

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1. National Renewable Energy Lab. (NREL), Golden, CO (United States)

The development of compositionally graded buffer layers (CGBs) with enhanced transparency would enable novel five and six junction solar cells, with efficiencies approaching 50% under high concentration. Here, we demonstrate highly transparent grades between the GaAs and InP lattice constants on both A- and B-miscut GaAs substrates, employing Al_xGayIn_1-x-yAs and highly Se-doped Burstein-Moss (BM) shifted Ga_xIn _1-xP. Transparency to >810 and >890 nm wavelengths is demonstrated with BM-shifted Ga_xIn_1-xP on B-miscut substrates and Al_xGayIn_1-x-yAs/Ga_xIn_1-xP(Se) combined grades on A-miscut substrates, respectively. 0.74 eV GaInAs solar cells grown on these transparent CGBs exhibit Woc = 0.41 V at mA/ cm², performance comparable with the state-of-the-art Ga_xIn_1-xP grade employed in the four-junction-inverted metamorphic multijunction (IMM) cell. A GaAs/0.74cV GaInAs tandem cell was grown with a transparent BM-shifted Ga_xIn_1-xP CGB to verify the CGB performance in a multijunction device structure. Quantum efficiency measurements indicate that the CGB is completely transparent to photons below the GaAs bandedge, validating its use in 4-6 junction IMM devices with a single-graded buffer. Furthermore, this tandem represents a highly efficient two-junction band gap combination, achieving 29.6% ± 1.2% efficiency under the AM1.5 global spectrum, demonstrating how the additional transparency enables new device structures.

• Research Organization: National Renewable Energy Lab. (NREL), Golden, CO (United States)
• Sponsoring Organization: USDOE Office of Energy Efficiency and Renewable Energy (EERE), Renewable Power Office. Solar Energy Technologies Office
• Grant/Contract Number: AC36-08GO28308
• OSTI ID: 1342505
• Report Number(s): NREL/JA-5J00-66503
• Journal Information: IEEE Journal of Photovoltaics, Vol. 7, Issue 1; ISSN 2156-3381
• Publisher: IEEE
• Country of Publication: United States
• Language: English

Related Subjects

14 SOLAR ENERGY
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
photovoltaic cells
III-V semiconductor materials
semiconductor epitaxial layers
semiconductor device doping