A new approach to the surface photovoltage method is demonstrated on thick
undoped microcrystalline silicon films grown on different substrates. The m
odel, which includes top as well as bottom space-charge regions, gives a go
od picture of rather complex experiments and allows good fitting of theoret
ical curves to experimental results. This method gives us not only the diff
usion length of minority carriers but also information on the existence and
properties of the space-charge regions in the sample and the results are v
erified by comparison with the standard procedure.