Light-trapping concentrator cells

Technical Report · Wed Nov 01 04:00:00 EST 1989

DOI:https://doi.org/10.2172/5231774· OSTI ID:5231774

Keavney, C. J.; Geoffroy, L. M.; Sanfacon, M. M.; Tobin, S. P. ^[1]

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1. Spire Corp., Bedford, MA (USA)

The objective of this project was to develop a thin, light-trapping silicon concentrator solar cell using a new structure, the cross-grooved cell. A process was developed for fabricating V-grooves on both sides of thin silicon wafers, the grooves on one side being perpendicular to those on the other side. A novel way of minimizing flat spots at the tops of the V-grooves was discovered. We experimentally verified the theoretical light-trapping superiority of the cross-grooved structure. We also demonstrated a reduction in grid line obscuration for grid lines running parallel to the V-grooves due to light reflection into the cell. high short-circuit current densities were achieved for p-i-n concentrator cells with the cross-grooved structure, proving the concept. The best efficiencies achieved were 18% at concentration, compared to 20% for a conventional planar low-resistivity cell. Recombination in the full-area emitter was identified as the major intrinsic loss mechanism in these thin, high-resistivity bifacial cells. Recombination on the emitter limits Voc and fill factor, and also leads to a large sublinearity of short-circuit current with light intensity. Reduction of the junction area is a major recommendation for future work. In addition, there were persistent problems with ohmic contacts and maintaining high minority-carrier lifetime during processing. We believe that these problems can be solved, and that the cross-grooved cell is a viable approach to the limit-efficiency silicon solar cell. This report covers research conducted between March 1987 and July 1989. 22 refs., 40 figs., 24 tabs.

• Research Organization: Sandia National Labs., Albuquerque, NM (USA); Spire Corp., Bedford, MA (USA)
• Sponsoring Organization: DOE/CE
• DOE Contract Number: AC04-76DP00789
• OSTI ID: 5231774
• Report Number(s): SAND-89-7092; ON: DE90004988
• Country of Publication: United States
• Language: English

Related Subjects

14 SOLAR ENERGY
141000* -- Solar Collectors & Concentrators
ANNEALING
CONCENTRATOR SOLAR CELLS
DATA
DEMONSTRATION PROGRAMS
DESIGN
DIRECT ENERGY CONVERTERS
DOPED MATERIALS
EFFICIENCY
ENERGY EFFICIENCY
EQUIPMENT
EVAPORATION
EXPERIMENTAL DATA
FABRICATION
FREQUENCY ANALYSIS
HEAT TREATMENTS
INFORMATION
INTERFACES
LABORATORY EQUIPMENT
LIGHT TRANSMISSION
MATERIALS
MEASURING METHODS
MEMORY DEVICES
METALLOGRAPHY
MIRRORS
NUMERICAL DATA
OPTICAL PROPERTIES
OPTICAL SYSTEMS
PERFORMANCE TESTING
PHASE TRANSFORMATIONS
PHOTOELECTRIC CELLS
PHOTOVOLTAIC CELLS
PHYSICAL PROPERTIES
PLANNING
RECOMBINATION
REFLECTIVITY
SEMICONDUCTOR DEVICES
SEMICONDUCTOR STORAGE DEVICES
SILICON SOLAR CELLS
SOLAR CELLS
SOLAR EQUIPMENT
SPECTROPHOTOMETRY
SURFACE PROPERTIES
TESTING