InP-Based Quantum Dots Having an InP Core, Composition-Gradient ZnSeS Inner Shell, and ZnS Outer Shell with Sharp, Bright Emissivity, and Blue Absorptivity for Display Devices

Indium phosphide (InP) has been regarded as the most promising composition of visible quantum dot (QD) emitters for the application to next-generation display devices primarily because of its environmental benignity. Bright, sharp emissivity of InP QDs should be pursued for the realization of high-efficiency, wide-color gamut display devices. Photoluminescence (PL) performance of InP QDs has been greatly improved based on synthetic advances enabling the securement of core size homogeneity and the formation of exquisite core/shell heterostructure. Until now, high-quality fluorescent InP QDs have been attainable exclusively through the use of a hazardous phosphorus (P) precursor of tris(trimethylsilyl)phosphine ((TMS)3P) against green chemistry. In this work, we report a synthetic breakthrough of green InP QDs toward narrow, bright emissivity by using a much cheaper, safer P alternative of tris(dimethylamino)phosphine ((DMA)3P). For this, QD synthesis proceeds via a so-called two-step approach, where as-grown InP cores are subjected to a stepwise size fractionation process and then placed in the consecutive double shelling of a composition-gradient ZnSexS1–x inner and a ZnS outer shell. The chemical composition (x) of the ZnSexS1–x inner shell in the range of 0.09–0.36 is varied to explore its effects on PL quantum yield (QY), size, and blue excitation light absorptivity. Because of the effective core size fractionation and elaborately designed heterostructure, the resulting InP/ZnSexS1–x/ZnS QDs exhibit exceptional green (527 nm) PL features of a sharp line width of 37 nm and a high PL QY of 87%, which have not been achievable to date from non-(TMS)3P-based QDs, when an optimal inner shell composition is applied.