InP/ZnS/ZnS Core/Shell Blue Quantum Dots for Efficient Light‐Emitting Diodes

Abstract As the concerns about using cadmium‐based quantum dots (QDs) in display are growing worldwide, InP QDs have drawn much attention in quantum dot light‐emitting diodes (QLEDs). However, pure blue InP based QLED has been rarely reported. In this work, first of all, pure blue InP/ZnS QDs with emission wavelength of 468 nm and quantum yield of 45% are synthesized. Furthermore, zinc oleate and S‐TOP are used as precursors to epitaxially grow the second ZnS shell. The residual zinc stearate reacted with S‐TOP to form ZnS shell, which increased the thickness and stability of QDs. Moreover, as the residual precursor of zinc stearate is removed, the current density increased from 13 mA cm −2 to 121 mA cm −2 at 8 V for the hole only device. External quantum efficiency increased from 0.6% of InP/ZnS QLED to 1.7% of InP/ZnS/ZnS QLED.