Synthesis of blue emitting InP/ZnS quantum dots through control of competition between etching and growth

Abstract

Blue (<480 nm) emitting Cd-free quantum dots (QDs) are in great demand for various applications. However, their synthesis has been challenging. Here we present blue emitting InP/ZnS core/shell QDs with a band edge emission of 475 nm and a full width at half maximum of 39 nm (215 meV) from their quantum confined states. The drastic temperature drop immediately after mixing of the precursors and holding them at a temperature below 150 degrees C was the critical factor for the synthesis of blue emitting QDs, because the blue QDs are formed by the etching of ultra-small InP cores by residual acetic acid below 150 degrees C. Etching was dominant at temperatures below 150 degrees C, whereas growth was dominant at temperatures above 150 degrees C. ZnS shells were formed successfully at 150 degrees C, yielding blue emitting InP/ZnS QDs. The colour of the InP/ZnS QDs depicted on the CIE 1931 chromaticity diagram is located close to the edge, indicating a pure blue colour compared to other InP-based QDs.