Thiol treatment to enhance photoluminescence and electroluminescence of CdSe/CdS core–shell quantum dots prepared by thermal cycling of single source precursors

Abstract

Stable and high photoluminescence quantum-yield CdSe/CdS core–shell quantum dots (QDs) with a zinc blende (ZB) structure in both the core and the shell are prepared by over-coating CdSe core nanocrystals with a controlled number of CdS monolayers (MLs). The epitaxial growth reaction is induced via the temperature cycling of a single-source precursor, namely cadmium diethyldithiocarbamate (Cd(DEDTC)₂), in oleylamine (OLA) and 1-octadecene (ODE) at temperatures between 140 and 200 °C. The quantum yield of the resulting core–shell quantum dots is then enhanced by means of a ligand exchange process with alkanethiol. The ligand-protected CdSe/CdS core–shell QDs are spin coated on an indium tin oxide (ITO)-glass substrate to form a type-I QD light-emitting device (QD-LED). It is shown that the QD-LED has a current efficiency of 0.22 cd A⁻¹. Notably, the current efficiency is 4.5 times higher than that of a QD-LED incorporating non-thiol-protected QDs, and is comparable to the best reported performance for type-I QD-LED devices in the literature.