High Efficiency Triple-Junction Amorphous Silicon Alloy Photovoltaic Technology, Final Technical Report, 6 March 1998 - 15 October 2001

Technical Report · Thu Nov 08 04:00:00 EST 2001

DOI:https://doi.org/10.2172/789084· OSTI ID:789084

Guha, S

This report describes the research program intended to expand, enhance, and accelerate knowledge and capabilities for developing high-performance, two-terminal multijunction amorphous silicon (a-Si) alloy cells, and modules with low manufacturing cost and high reliability. United Solar uses a spectrum-splitting, triple-junction cell structure. The top cell uses an amorphous silicon alloy of {approx}1.8-eV bandgap to absorb blue photons. The middle cell uses an amorphous silicon germanium alloy ({approx}20% germanium) of {approx}1.6-eV bandgap to capture green photons. The bottom cell has {approx}40% germanium to reduce the bandgap to {approx}1.4-eV to capture red photons. The cells are deposited on a stainless-steel substrate with a predeposited silver/zinc oxide back reflector to facilitate light-trapping. A thin layer of antireflection coating is applied to the top of the cell to reduce reflection loss. The major research activities conducted under this program were: (1) Fundamental studies to improve our understanding of materials and devices; the work included developing and analyzing a-Si alloy and a-SiGe alloy materials prepared near the threshold of amorphous-to-microcrystalline transition and studying solar cells fabricated using these materials. (2) Deposition of small-area cells using a radio-frequency technique to obtain higher deposition rates. (3) Deposition of small-area cells using a modified very high frequency technique to obtain higher deposition rates. (4) Large-area cell research to obtain the highest module efficiency. (5) Optimization of solar cells and modules fabricated using production parameters in a large-area reactor.

• Research Organization: National Renewable Energy Lab., Golden, CO (US)
• Sponsoring Organization: US Department of Energy (US)
• DOE Contract Number: AC36-99GO10337
• OSTI ID: 789084
• Report Number(s): NREL/SR-520-31290
• Country of Publication: United States
• Language: English

Related Subjects

14 SOLAR ENERGY
36 MATERIALS SCIENCE
AMORPHOUS SILICON (A-SI) ALLOY CELLS
AMORPHOUS STATE
ANTIREFLECTION COATINGS
DESIGN
ENERGY GAP
FABRICATION
GERMANIUM ALLOYS
MANUFACTURING
MODIFIED VERY-HIGH-FREQUENCY TECHNIQUE
PV
QUANTUM EFFICIENCY
RADIO FREQUENCY TECHNIQUE
SILICON SOLAR CELLS
SPECTRUM-SPLITTING
TRIPLE-JUNCTION CELL STRUCTURE
TWO-TERMINAL MULTIJUNCTION