Development of high-efficiency solar cells on silicon web. Fourth quarterly progress report, January-March 1985

Technical Report · Mon Apr 01 04:00:00 EST 1985

DOI:https://doi.org/10.2172/5886539· OSTI ID:5886539

Rohatgi, A.; Meier, D. L.; Campbell, R. B.

This monthly report discusses a novel approach to high-efficiency silicon solar cells in which the cell designs consist of doped polysilicon regions in the emitter and/or in the grid regions of the solar cells. These designs should work more effectively for cells in which V/sub oc/ is limited by emitter recombination. The n/sup +/ polysilicon emitter is believed to lower hole mobility and bandgap narrowing compared to a single-crystal silicon emitter, thus reducing the emitter contribution to the reverse saturation current and giving higher V/sub oc/. Polysilicon deposition and POCl/sub 3/ diffusion conditions have been developed for poly emitter solar cells, and solar cells have actually been fabricated according to one of the designs. In these cells, polysilicon grid lines were defined by ion-milling and polysilicon was removed from the remainder of the emitter. Preliminary results indicate that the heat treatment subsequent to ion-milling resulted in a loss of carrier lifetime, partly because of a lower than expected V/sub oc/. In the first run, V/sub oc/ of the cells was at most equal to that of the conventional cells, where no poly deposition was performed and the dopant surface concentration on the emitter was 2 x 10/sup 20/cm/sup -3/. More experiments are in progress to preserve carrier lifetime and optimize the polysilicon emitter design for high-efficiency cells. Model calculations were also done in this period to determine the resistivity and diffusion length requirements for achieving 17 to 18% efficient web cells. Calculations indicate that a combination of front- and back-surface passivation and double-layer AR coating will give 17.5% efficient cells on 4 ohm-cm, 150 ..mu..m thick web crystals only when the minority carrier diffusion length becomes 467 ..mu..m. However, a diffusion length of only 125 ..mu..m will be required to achieve 17.5% efficient web cells if the bulk resistivity is dropped from 4 ohm-cm to 0.2 ohm-cm.

• Research Organization: Westinghouse Research and Development Center, Pittsburgh, PA (USA)
• DOE Contract Number: NAS-7-100-956786
• OSTI ID: 5886539
• Report Number(s): DOE/JPL/956786-85/4; ON: DE85012360
• Country of Publication: United States
• Language: English

Related Subjects

14 SOLAR ENERGY
140501* -- Solar Energy Conversion-- Photovoltaic Conversion
CARRIER LIFETIME
DIRECT ENERGY CONVERTERS
ELECTRIC CONDUCTIVITY
ELECTRICAL PROPERTIES
EQUIPMENT
FABRICATION
LIFETIME
MATHEMATICAL MODELS
PHOTOELECTRIC CELLS
PHOTOVOLTAIC CELLS
PHYSICAL PROPERTIES
SILICON SOLAR CELLS
SOLAR CELLS
SOLAR EQUIPMENT
TESTING