There are literature reports saying that there can be multi exciton formation with high intense light (laser)...But there are reports ( from Gregory D scholes) of dual emission recorded from fluoresence spectrometer in the case of hetero nanostructures...I believe that, to make dual emission when we excite at single wavelenth must have more than one exciton formation...
it's depend your semiconducteur ,if you have two photon absorption or no ,if it's the case , you have two exciton . or you have for every photon one exciton .
it's depend the gap of your semiconductor and the wavelength excitation
thank you Z.ben for the reply and I agree with you...at the excitation wavelength both the nanoblock (of heterostructure) is getting excited since both have absorption at that region...one more thing when it forms core/shell or diblock hetero nanostructure the band gap will shift and in most of the core/shell structure we see only the band edge emission. In our case we are dealing with one dimensional diblock structure where we are seeing dual emission...that is why i have doubt regarding the number of exciton formation.