Hole intraband relaxation and the exciton radiative lifetime in CdSe quantum dots

Summary form only given. Colloidal synthesis allows preparation of almost monodispersed 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 energy structures 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 competition between radiative and nonradiative decay channels. In the present work, we apply femtosecond (fs) photoluminescence (PL) and transient absorption (TA) spectroscopies to study carrier relaxation dynamics in CdSe QDs and in particular to derive a radiative lifetime of the lowest exciton state.