Absorption cross-section and related optical properties of colloidal InAs quantum dots.

We report the absorption cross-section of colloidal InAs quantum dots of mean radii from 1.6 to 3.45 nm. We find excellent agreement between the measured results and calculated values based on a model of small-particle light absorption. The absorption cross-section per dot is 6.2 x 10(-16)R(3) cm(2) at 2.76 eV and 3.15 x 10(-16)R(1.28) cm(2) at the first-exciton absorption peak, with the dot radius R in nm. We find that the per-quantum-dot particle oscillator strength of the first-exciton transition is constant for all sizes studied. The radiative lifetime of the first exciton calculated from the oscillator strength increases with dot size and ranges from 4 ns for the smallest dots to 14 ns for the largest ones.