Finite-Size Effect on Band Structure and Photoluminescence of Semiconductor Nanocrystals

Based on a model for size-dependent atomic cohesive energy of nanocrystals, a simple and unified model, without any adjustable parameter, has been established for finite size effect on shifts of valence and conduction band edges [DeltaE_V(D) and DeltaE_C(D)], and bandgap expansion [DeltaE_G(D)| of semiconductor nanocrystals, where Delta denotes the expansion and D is the size of nanocrystals. In the light of this model, DeltaE_V(D), DeltaE_C(D), and DeltaE_G(D) functions increase with dropping D in comparison with the corresponding bulk counterparts. The available experimental results of Si, CdS, ZnSe, and ZnTe nanocrystals confirm the validity of model.