Nanometer-size colloidal semiconductor nanocrystals, or Quantum Dots (NQD), are very prospective active centers
because their light emission is highly efficient and temperature-independent. Nanocomposites based on the incorporation
of QDs inside a polymer matrix are very promising materials for application in future photonic devices because they
combine the properties of QDs with the technological feasibility of polymers. In the present work some basic
applications of these new materials have been studied. Firstly, the fabrication of planar and linear waveguides based on
the incorporation of CdS, CdSe and CdTe in PMMA and SU-8 are demonstrated. As a result, photoluminescence (PL) of
the QDs are coupled to a waveguide mode, being it able to obtain multicolor waveguiding. Secondly, nanocomposite
films have been evaluated as photon energy down-shifting converters to improve the efficiency of solar cells.