Dear Fereshte Tavakkoli,

I see 2 ways of do it:

1) calculate the Rayleigh scattering curve and adjust manually the parameters for the best fit and in the end subtract it to the photoluminescence spectrum.

2) from the photoluminescence spectrum you can select the Rayleigh scattering by remove all the other features. Then you can make a automatic fit to the Rayleight scattering and remove it from the original photoluminescence spectrum.