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Published online by Cambridge University Press: 27 February 2012
Exchanging the original organic ligands of colloidal CdSe quantum dots (QDs) with metal chalcogenide SnS4 ligands resulted in absorption peak redshifts and complete photoluminescence quenching in QD solids. The ITO/QDs/Al structure with SnS4-capped QDs showed much higher electrical conductivity and reduced space-charge limited current. These results are indicative of carrier delocalization as well as enhanced inter-QD electronic coupling caused by the inorganic ligands. The SnS4-capped QDs were able to retain strong excitonic absorption. The photocurrent spectral response of the all-inorganic QD film resembled its absorption spectra, and was three orders of magnitude stronger than that of QDs with organic ligands. It was found that mild annealing at ∼ 200 oC transformed the SnS4-capped QD film into to a more conductive assembly, degrading its absorption and photocurrent generation. These findings suggest that colloidal QDs with metal chalcogenide ligands are better suited for solar energy conversion and photodetection than use in light-emitting devices as luminophores.