Evidence for reversible oxygen ion movement during electrical pulsing: enabler of the emerging ferroelectricity in binary oxides

The performance of red InP and blue ZnTeSe-based quantum dots (QDs) and corresponding QD light emitting diodes (QLEDs) has already been improved significantly, whose external quantum efficiencies (EQEs) and luminances have exceeded 20% and 80,000 cd m-2, respectively. However, the inferior performance of the green InP-based device hinders the commercialization of full-color Cd-free QLED technology. The ease of oxidation of the highly reactive InP cores leads to high non-radiative recombination and poor photoluminescence quantum yield (PL QY) of the InP-based core/shell quantum dots (QDs), limiting the performance of the relevant QLEDs. Here, we proposed a fluoride-free synthesis strategy to in-situ passivate the InP cores, in which zinc myristate reacted with phosphine dangling bonds to form Zn-P protective layer and protect InP cores from the water and oxygen in the environment. The resultant InP/ZnSe/ZnS core/shell QDs demonstrated a high PL QY of 91%. The corresponding green-emitting electroluminescence devices exhibited a maximum EQE of 12.74%, along with a luminance of over 175,000 cd m^-2 and a long T₅₀@100 cd m^-2 lifetime of over 20,000 h.