Complementary transport channels in Si-ZnS nanocomposites: first principles simulations

In solar energy conversion devices, nanoparticles (NPs) are often embedded in solid matrices, either crystalline or amorphous. At present a detailed understanding of the influence exerted by the embedding matrix on the absorption of sunlight by the nanoparticle, and the role of the nanoparticle-matrix interface remain elusive. We investigated Si NPs embedded in ZnS, a system that was used as a charge transport layer in recent experiments. A realistic model of the NP-matrix interface was created from ab-initio molecular dynamics simulations. We found that this nanocomposite exhibits complementary transport channels, where electron transport occurs by hopping between NPs and hole transport through the ZnS-matrix. In analogy to Si NPs embedded in SiO2 [1] we found a strong gap reduction and corresponding red-shifted optical absorption, caused by chemical shifts at the NP-matrix interface. \\[4pt] [1] T. Li, F. Gygi, G. Galli, Phys. Rev. Lett. 107, 206805 (2011)