A silane composition for preparing a semiconductor thin films of a solar
cell is disclosed. The silane composition contains a polysilane compound
represented by the formula Si.sub.nR.sub.m (n is an integer of 3 or more,
m is an integer of n to (2n+2) and an m number of R's are each
independently a hydrogen atom, alkyl group, phenyl group or halogen atom,
with the proviso that when all the m number of R's are hydrogen atoms and
m=2n, n is an integer of 7 or more), and at least one silane compound
selected from cyclopentasilane, cyclohexasilane and
silylcyclopentasilane.