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

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/ cm 2, 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, demonstratingmore » how the additional transparency enables new device structures.« less
Authors:
 [1] ;  [1] ;  [1]
  1. National Renewable Energy Lab. (NREL), Golden, CO (United States)
Publication Date:
OSTI Identifier:
1342505
Report Number(s):
NREL/JA-5J00-66503
Journal ID: ISSN 2156-3381
Grant/Contract Number:
AC36-08GO28308
Type:
Accepted Manuscript
Journal Name:
IEEE Journal of Photovoltaics
Additional Journal Information:
Journal Volume: 7; Journal Issue: 1; Journal ID: ISSN 2156-3381
Publisher:
IEEE
Research Org:
National Renewable Energy Lab. (NREL), Golden, CO (United States)
Sponsoring Org:
USDOE Office of Energy Efficiency and Renewable Energy (EERE), Solar Energy Technologies Office (EE-4S)
Country of Publication:
United States
Language:
English
Subject:
14 SOLAR ENERGY; 71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; photovoltaic cells; III-V semiconductor materials; semiconductor epitaxial layers; semiconductor device doping