Size dependent femtosecond electron cooling dynamics in CdSe quantum rods

Electronic relaxation dynamics of photoexcited CdSe quantum rods have been studied with femtosecond transient absorption spectroscopy. Samples with the same length, similar to30 nm, but with different diameters, 2.5 and 8.0 nm, were investigated. We found that the intraband energy relaxation is about 8 times faster in the thin rods than in the thick ones. A comparison is made between relaxation dynamics in quantum rods and dots, and different relaxation mechanisms are discussed.