Overcoming side reaction effects in the colloidal synthesis of ZnSe/ZnS core/shell quantum dots with an etching strategy

The potential use of large-size ZnSe quantum dots as blue emitters for display applications has greatly inspired the colloidal synthesis. Herein, we report the negative effects of side reactions of large-size ZnSe quantum dots. The side reactions between oleic acid and oleylamine generated amidation products and H2O, which led to the hydrolysis of Zn(OA)2 to Zn(OH)2 and the subsequent formation of zinc oxide (ZnO) and zinc bis[diphenylphosphinate] (Zn(DPPA)2) precipitates. These side reactions resulted in the formation of a defective surface including a Se-rich surface and oxygen-related defects. Such negative effects can be overcome by adopting an etching strategy using potassium fluoride and myristic acid in combination. By overcoating a ZnS shell, blue emissive ZnSe/ZnS quantum dots with a maximum photoluminescence quantum yield of up to 91% were obtained. We further fabricated ZnSe quantum dots-based blue light-emitting diodes with an emission peak at 456 nm. The device showed a turn-on voltage of 2.7 V with a maximum external quantum efficiency of 4.2% and a maximum luminance of 1223 cd<middle dot>m-2.