  We report on the effect of ligand exchange of copper sulphide selenide as
well as copper selenide nanocrystals with the organic pi-system Cobalt
beta-tetraaminophthalocyanine and analyse changes in the structural, optical as
well as electric properties of thin films of these hybrid materials. A strong
ligand interaction with the surface of the nanocrystals is revealed by UV-vis
absorption and Raman spectroscopy. Grazing-incidence small-angle X-ray
scattering studies show a significant contraction in the interparticle distance
upon ligand exchange. For copper-deficient copper selenide, this contraction
has a negligible effect on electric transport, while for copper-deficient
copper sulphide selenide, the conductivity increases by eight orders of
magnitude and results in metal-like temperature-dependent transport. We discuss
these differences in the light of varying contributions of electronic vs. ionic
transport in the two materials and highlight their effect on the stability of
the transport properties under ambient conditions. With photocurrent
measurements, we demonstrate high optical responsivities of 200-400 A W-1 for
the phthalocyanine-capped copper sulphide selenide and emphasize the beneficial
role of the organic pi-system in this respect, which acts as an electronic
linker and an optical sensitizer at the same time.
