Ligand Control of Semiconductor Nanocrystals for Efficient Carrier Injection

Abstract

ABSTRACTInorganic/organic hybrid material of CdSe/ZnS core/shell nanocrystals (NCs) covered with organic ligands was prepared with ligand exchange reaction in order to facilitate carrier injection into NCs through the organic ligands. The organic ligands used in this study, 2-naphtalenethiol and bathophenanthroline, were selected as model compounds according to adjustment of highest occupied molecular orbital and lowest unoccupied molecular orbital of the ligand to valence band maximum and conduction band minimum of the CdSe NCs, respectively. The prepared hybrid NCs easily disperse in polar organic solvents such as CHCl3 and show photoluminescence only from the CdSe/ZnS core/shell NCs. Current-voltage characteristics of the ligand exchanged NCs thin films sandwiched between electrodes were investigated. It was shown that conductivity of the film was improved by the introduction of carrier injecting ligands in comparison to the ligand unexchanged trioctylphosphine oxide-capped CdSe/ZnS NC thin film.