Femtosecond interactions in semiconductor quantum dots

Colloidal synthesis allows preparation of almost monodisperse semiconductor nanoparticles with sizes from 1 to 10 nm and size dispersions as small as 5%. These nanoparticles are also known as nanocrystals or colloidal quantum dots (QDs). The sub-10-nm size range corresponds to a regime of strong quantum confinement for which electronic energies exhibit a pronounced dependence on particle size. Tunable electronic structures combined with the ease of chemical manipulation, make colloidal QDs ideal building blocks for electronic and optical nanodevices. An important step towards realization of such devices is development of understanding of carrier relaxation processes in QDs and in particular the effect of QD size and surface properties on intra-band energy relaxation, competition between radiative and nonraditive decay channels, and multiparticle dynamics. In the present work, we apply femtosecond photoluminescence and transient absorption spectroscopies to investigate carrier relaxation in strongly-confined CdSe QDs