Patent ID: 8709858

Claim:
A process for reducing or eliminating the band gap shift in the production of a photovoltaic system, said production process comprising: oligomerizing or polymerizing a mixture comprising a silane and a germanium compound to form a formulation comprising the silane, the germanium compound and a co-oligomerized product consisting of units of the silane and the germanium compound; coating a flat surface of a substrate with the formulation, wherein during the coating the formulation is in liquid form, to obtain a coated substrate, irradiating, thermally treating, or both irradiating and thermally treating the coated substrate to obtain an at least partially polymorphic layer comprising silicon and germanium on the flat surface of the substrate; wherein the germanium compound is of formula Ge n H 2n+2 or Ge n H 2n where n is an integer from 4 to 8 and is present in the mixture with an oligomeric germanium compound of formula Ge n R 2n+2 or Ge n R 2n and having weight-average molecular weight of 500 to 10,000 g/mol, wherein n is an integer from 4 to 8, R is independently H, halogen, or organyl, and at least one R is an organyl, wherein the silane is of formula (i) Si n H 2n+2 where n is an integer from 3 to 10, (ii) Si n H 2n where n is an integer from 4 to 8, (iii) Si n R 2n+2 where n is an integer from 8 to 100 and R is H or an organyl with at least one R being an organyl, or (iv) Si n R 2 where n is an integer from 8 to 100 and R is H or an organyl with at least one R being an organyl.