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