Organic–inorganic hybrid composites for photovoltaics: Organic guest molecules embedded in μc-Si and ZnSe host matrices

The concept of organic–inorganic hybrid composites for bulk sensitization of inorganic semiconductors by organic dye molecules is introduced. The idea is either to increase the absorptivity of e.g. indirect semiconductors as μc-Si or to expand in a two-step process the absorption spectrum of wide gap semiconductors to photons of energy smaller than the band gap. The composites are prepared by vacuum-based codeposition. Raman and optical spectroscopy, and photoemission have been used to prove the stability of the organic molecules ZnPc and F₁₆ZnPc for the applied growth conditions. Enhancement of photoconductivity has been shown for ZnPc–Si bilayer. As a crucial parameter for the transfer of excited charges, the alignment of dye HOMO–LUMO states versus semiconductor band edges has been determined using photoelectron spectroscopy.