Abstract

Photovoltaic characteristics of homoepitaxial solar cells on specially prepared upgraded metal lurgical-grade polysilicon substrates were measured. Good spectral responsivity values obtained in the long-wavelength region, despite poor absorption of long-wavelength radiation in the 20-μm thick epilayers, led to the inference of enhanced optical paths in the epilayers for the incident radiation. A likely mechanism for these long optical paths is surface texture often exhibited by silicon epitaxial films and seen on the samples studied. Measured minority carrier diffusion lengths of 30–40 μm and epilayer thickness of 20 μm represented conditions in which a back surface field in the substrate also contributed effectively to the performance of the cells, which, even for entirely nonoptimized fabrication parameters, yielded AM 1.5 efficiencies of the order of 7%.

© 1987 Optical Society of America