In my opinion, it is not easy to adjust the bands of the graphene, especially in the visible range. So I don't think we can replace the photonic crystals by the grephene.

If you insert a very thin graphene layer inside a PC it will affect its transmittance e.g. will cause a decrease in the field due to the graphene layer. In the calculation you have to consider the graphene conductivity into account. 

Dear Tamer,

can you give more information about your goel? This may help you answer your question.

Kind regards, Patrick