Article link:http://pubs.rsc.org/en/content/articlelanding/2018/nr/c7nr09175c#!divAbstract

In this work, we report a facile and robustsynthesis ofZnCdS core/shell quantum dots (QDs) with thick Cd_xZn_1−xS (x =constant) uniform alloys as intermediate shell which can provide effective confinement of excitons within the ZnCdS cores and ultrathin ZnS outermost shell to improve stability by epitaxy growth at a relatively high temperature. The resulting nearly monodisperse ZnCdS/Cd_xZn_1−xS/ZnS core/shell QDs havehigh photoluminescence quantum yield (near to 100%), high color purity (full width at half maximum (FWHM) <18 nm). More importantly, theZnCdS/Cd_xZn_1−xS/ZnS core/shell QDs have good chemical/photochemicalstability and more efficientcarrier transport performance compared with ZnCdS/ZnS core/shell QDs.

Two types of QDs of ZnCdS/ZnS and ZnCdS/Cd_xZn_1−xS/ZnS were incorporated into the solution-processed hybrid QD-based light-emitting devices structure as emissive layer. We find that the presence of Cd_xZn_1−xS shell makes a profound impact on device performances such as external quantum efficiency and current efficiency. The corresponding light-emitting diodes exhibited a high EQE exceeding 18%, a peak current efficiency of 3.4 cd A^-1and low efficiency roll-off.Such excellent results of ZnCdS/Cd_xZn_1−xS/ZnS based QLED are likely attributable to the QD‘s high PL QY and very thin ZnS outermost shell which did notsacrifice charge injection efficiency in QLED.