Photoluminescence and its decay of the dye/porous-silicon composite system

Photoluminescence (PL) and its decay in the composite system of dye/porous silicon, consisting of oxidized porous silicon (PSi) and impregnated dyes, have been studied. We find that the PL spectra of the dyes are similar to that of dyes in ethanol solution while being quite different from those of dye films absorbed on the surface of c-Si. The line shape of the spectra is more symmetric for impregnated dyes than that in solution. The PL decay of the impregnated dyes has been measured. The lifetime is about 100 ps for rhodamine B impregnated in as-prepared PSi and it becomes much shorter for that in the annealed PSi layers. The influence of absorbed dyes on the PL decay of PSi has also been measured. It shows that impregnated dyes provide new nonradiative processes for the deactivation of the excited PSi. (C) 1996 American Institute of Physics.