Relating photovoltaic output and spectral response of amorphous, polycrystalline, ribbon, epitaxial and single-crystal MIS solar cells

Spectral response and diffusion length characteristics of the various MIS cells developed at Rutgers and previously reported in the literature have been investigated. The cells, designated according to the type of Si substrate used, appear in the following descending order based on the above studies: (1) Monsanto single-crystal Si with a peak quantum efficiency (Q.E.) of 87.4% and a diffusion length (L
n
) of 70 µm, (2) Wacker polycrystalline Si, peak Q.E. = 82.8%, L
n
= 60 µm, (3) IBM ribbon Si, (4) Epitaxial Si, (5) Mobil-Tyco EFG ribbon Si and (6) amorphous Si. The Q.E. of the Monsanto Si base-line cell is shown to be adequately explained in terms of the wavelength dependence of the collection efficiency and the transmittance of the barrier metal. Good agreement is also shown between theoretical and experimental plots of short-circuit current density (J
sc
) versus L
n
. The Wacker cell shows best short wavelength response of all the cells studied including a commercial p-n cell having a peak Q.E. of 100% and L
n
= 184 µm.