The relaxation dynamics of the charge carriers in copper-based semiconductor quantum dots were investigated using femtosecond time-resolved pump-probe spectroscopy. It was found that copper oxide quantum dots show significantly longer carrier lifetimes (> 117 ps and a nanosecond component) compared to the copper sulfides (< 25 ps). This is probably due to a more perfect surface structure and less trapping in the copper oxide system. Both quantum dot materials seem to be interesting for solar cell applications based on the presented study. © 2005 The Electrochemical Society. All rights reserved.