We performed visible photoluminescence and scanning electron micrograph mea
surements on several porous poly-Si/Si and a-Si/Si structures. We found tha
t the porous interfacial layer between the thin film and the substrate dete
rmined the optoelectronic properties for the structures. With the results,
we present a model for porous structures based on the quantum confinement e
ffect in silicon wires; the decreasing emission intensity and the redshift
of photoluminescence originate from the silicon wires in the porous interfa
ce formed during all electrochemical process.