Energy band mixing in core-shell-structured Si∕FeSi2 nanocomposites

Using the bandmixing model of direct and indirect gaps, we calculate the energy levels of electrons and holes confined in the Si∕FeSi2 nanocomposite consisting of nanocrystalline Si core, interfacial FeSi2 layer, and outer Fe2O3 crust. The obtained results explain very well the intensity enhancement and pinning behavior of the observed photoluminescence peaks after the nanocomposite is stored in air. We also theoretically obtain the photoluminescence excitation characteristics. Good agreement is achieved between the theory and experiments.