摘要： Multiple exciton generation (MEG) in semiconductor nanostructures is of great interest for the enhancement of related performances in optoelectronic devices and for the shape dependence of conversion ef?ciency with which absorbed photons are converted into electron-hole pairs. However, theoretical insight into the coupling effects from the size and shape gradient on the MEG and related optoelectronic properties at the atomic level remains unclear. Here, we investigate the MEG and optoelectronic properties in PbSe nanostructures with different morphologies (nanocrystals, nanowires, and nanocones) based on the bond relaxation correlation mechanism, detailed balance principle, and Fermi statistical theory. It is found that size reduction of nanostructures can increase the bandgap, suppress the threshold energy, and enhance the MEG ef?ciency. Moreover, optimal conversion ef?ciency of PbSe nanostructures can be achieved by modulating the geometrical parameters.