SIZE-DEPENDENT ELECTRON-HOLE EXCHANGE INTERACTION IN CDSE QUANTUM DOTS

We have investigated the fine structure of luminescence of CdSe nanocr ystals observed with size-selective excitation. We show that the lumin escence line closest to the laser arises from the recombination of the optically forbidden A-exciton. Radiative recombination occurs via a p honon-assisted virtual transition to the B-exciton state. The electron -hole exchange energy obtained from the experimental results strongly increases with decreasing nanocrystal size as expected from the increa sing overlap of the electron and hole wave functions. The size depende nce is in good agreement with the theoretical predictions.