Optical characterization of CdSe quantum dots with metal chalcogenide ligands in solutions and solids

The exchange of the original organic ligands of colloidal CdSe core and CdSe/CdS/ZnS core/multishell quantum dots (QDs) with inorganic metal chalcogenide ligands (SnS(4)(4-)) resulted in carrier delocalization in solutions and enhanced inter-QD electronic coupling in solids, as inferred from peak redshift and broadening of the absorption and photoluminescence (PL) spectra. The SnS(4)-capped QDs retained strong excitonic absorption but suffered significant PL quenching. Mild thermal treatment below 350 degrees C transformed the SnS(4) ligands into a more conductive phase, leading to stronger coupling yet complete PL quenching. These findings suggest that QD solids with metal chalcogenide ligands may have high quantum yields of photocurrent generation and can be used as functional blocks in thin-film solar cells for efficient solar energy conversion. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3610456]