Polymorphous hydrogenated silicon Schottky diodes: Properties under illumination

Abstract

This report describes the properties of thick Schottky diodes based on standard device grade amorphous hydrogenated silicon or polymorphous hydrogenated silicon under illumination. It has been observed that the internal collection efficiency in the red part of the spectrum is much higher for the polymorphous diodes than for the standard one. In contrast, at short wavelength there is no significant difference at short circuit, but the maximum output power and the fill factor are much higher in the case of polymorphous samples. Finally, the effect of reverse bias annealing has been examined. The experimental results are discussed, taking into account simulation studies in the literature. In particular it is shown that the collection efficiency at long wavelength is determined mainly by recombination in the bulk, and that the experimental data correlate with the electronic properties of films prepared in the same conditions. At short wavelength, recombination in the front layer seems to be an important carrier loss mechanism in standard diode at low forward bias, while it is negligible in polymorphous samples. Finally, the effect of reverse bias annealing is tentatively attributed to a widening of the valence band tail.