Study of non radiative relaxation and exciton-phonon coupling in colloidal CdTe quantum dots

In this contribution we present temperature and size dependence of the non radiative relaxation and exciton-phonon coupling in colloidal CdTe Quantum Dots (QDs). PL measurements as a function of the temperature show that the main non radiative process which limits the quantum efficiency at room temperature is the thermal escape, assisted by multiple LO phonons absorption. The number of phonons involved in the thermal escape and the exciton-phonon coupling strongly depend on the QDs size. In particular, the coupling constant with the acoustical phonons is strongly enhanced in QDs with respect to CdTe quantum well systems and bulk CdTe. On the contrary, the exciton-LO phonon interaction decreases as the degree of quantum confinement increases. © 2007 American Institute of Physics.