Fabrication of ternary and quaternary chalcogenide compounds based on Cu, Zn, Sn and Si for thin film photovoltaic applications

We investigated the use of ternary and quaternary chalcogenide compounds based on Cu, Zn, Sn and Si for use as high band gap absorber layers in thin film photovoltaics. We have investigated the fabrication of Cu₂Zn(Sn,Si)Se₄, Cu₂Si(S,Se)₃ and Cu₈Si(S,Se)₆ thin film layers. Whereas, Cu₂Zn(Sn,Si)Se₄ and Cu₂Si(S,Se)₃ appeared to be difficult to fabricate, because the Si did not intermix well with the rest of the elements at the typical process temperatures used for glass substrates, Cu₂ZnSiSe₄ and Cu₈Si(S,Se)₆ could be formed. The fabricated layers were polycrystalline with a typical thickness of about 1 μm. We also fabricated solar cells with the different absorber materials, using a standard Mo back contact and CdS/ZnO buffer layer combination, but despite very bright photoluminescence response of the Cu₈SiS₆ and Cu₈SiSe₆layers at an energy of about 1.84 and 1.3 eV respectively, the measured efficiencies remained below 0.1% due to particularly low photocurrents.