Size Dependence of Excitons in Silicon Nanocrystals

Two-particle calculations, which include the electron-hole Coulomb interaction nonperturbatively, are performed for excitons in surface passivated Si nanocrystals. The calculated exciton energies agree quantitatively with photoluminescence data. The exciton charge distributions differ markedly from those obtained in single-particle calculations. The two-particle calculations are compared with single-particle calculations which treat the Coulomb interaction perturbatively. The range of validity for the perturbative treatment of the Coulomb interaction is determined.