Inkjet-printed blue InP/ZnS/ZnS quantum dot light-emitting diodes

Abstract

Inkjet-printed quantum dot light-emitting diodes (QLEDs) are considered to be ideal candidates for use in full-color displays. However, preparation of eco-friendly blue InP QLEDs using inkjet printing techniques remains rather challenging due to the inferior optical properties of QDs. Here, we present the first efficient method for generating inkjet-printed QLEDs with high color purity using blue InP/ZnS/ZnS QDs as the emitting layer. A two-step heat-up and thick shell strategy was employed for the preparation of blue InP/ZnS/ZnS QDs with a photoluminescence (PL) peak at 465 nm, full width at half-maximum of 38 nm, and PL quantum yield (QY) of ∼ 96 %, which are the records for blue InP QDs. We found that the use of a zinc iodide precursor and anhydrous oxygen reaction environment is critical to determining InP core size, and the size distribution of InP cores can be improved by separating formation of InP magic size clusters and cores via a heat-up step at low temperature. We used two kind of zinc precursors to facilitate shell growth, and the engineered shell thickness suppresses energy transfer, enabling InP/ZnS/ZnS QDs film with high PLQYs and contributing to efficient inkjet printing of QLEDs. These results can facilitate the development of blue InP QLEDs for large-area electroluminescent full-color displays.