Silicon solar cell process development, fabrication and analysis. Fifth quarterly report, October 1, 1979-December 31, 1979

Abstract

This program investigates, develops and utilizes technologies appropriate and necessary for improving the efficiency of solar cells made from various unconventional silicon sheet materials. During this reporting period, work has progressed in fabrication and characterization of solar cells from EFG (RH) multi-ribbon, dendritic webs and cast silicon by HEM. Solar cells were fabricated using various process modifications, such as shallow junction formation, BSF, back surface reflector (BSR), surface etching and texturizing, gettering by mechanical damage and diffusion glass and grain boundary passivation. The solar cell parameters measured included open circuit voltage, short circuit current, curve fill factor, and conversion efficiency (all taken under AMO illumination). Additional measurements under AM1 conditions have been included, for direct evaluation and to collect information on the AM1/AM0 conversion factors for the various sheet materials. Also, measurement for typical cells included spectral response and minority carrier diffusion length. The obtained results were compared to the properties of cells made from conventional single crystalline Czochralski silicon with an emphasis on statistical-evaluation. Increased emphasis was given toward modifying the process to yield increased performance.