Abstract: The production of improved multiple cell photovoltaic amorphous silicon devices having improved wavelength threshold characteristics is made possible by adding one or more band gap adjusting elements to the silicon alloy material in one or more cells of the device. The adjusting element or elements are added at least to the active photoresponsive regions of constituent amorphous silicon cells, which regions preferably further include at least one of fluorine and hydrogen. One adjusting element is germanium which narrows the band gap from that of the silicon alloy materials without the adjusting element incorporated thereinto. Other adjusting elements can be used, such as carbon or nitrogen to widen the band gap. The silicon and adjusting elements are concurrently combined and deposited as amorphous silicon alloys by glow discharge decomposition techniques.