Size dependent development of band structure in semiconductor crystallites.

This manuscript summarizes a lecture given at the International Conference on Photochemical Conversion and Storage of Solar Energy. Size dependent development of bend structure is described within the simple Huckel approximation (tight binding theory), with the specific example of linear polyene chains. An effective mass level structure appears at the band extrema in finite length chains. The differing chemical natures (i.e., bonding, antibonding, and nonbonding) of molecular orbitals at different points in the Brillouin Zone are emphasized. This lecture provides a chemical background for understanding the size-dependent optical spectra of small semiconductor crystallites.