A study of CdS nanoparticle surface states by potential-modulated sub-bandgap spectroscopy

The potential modulation spectrum of CdS Q-dots deposited on an optically transparent electrode has been investigated. A peak at 580 nm, that corresponded to bleaching of a sub-bandgap absorption, was observed. It was established that the peak was related to electron injection into the conduction band of the CdS Q-dots. The mechanism by which the absorption of surface states may be monitored using potential-modulated absorption spectroscopy is outlined.