Vi. Klimov et al., Mechanisms for intraband energy relaxation in semiconductor quantum dots: The role of electron-hole interactions, PHYS REV B, 61(20), 2000, pp. R13349-R13352
To evaluate the role of nonphonon energy relaxation mechanisms in quantum d
ots and in particular the role of electron-hole (e-h) interactions, we have
studied femtosecond carrier dynamics in CdSe colloidal nanoparticles in wh
ich the e-h separation (coupling) is controlled using different types of su
rface ligands. In dots capped with hole accepting molecules, the e-h coupli
ng is strongly reduced after the hole is transferred to a capping group. By
re-exciting an electron within the conduction band at different stages of
hole transfer and monitoring its relaxation back into the ground state, we
observe a more than tenfold increase in the electron relaxation time (from
250 fs to 3 ps) after the completion of the hole transfer to the capping mo
lecule. This strongly indicates that electron relaxation in quantum dots is
dominated not by phonon emission but by the e-h energy transfer.