The photoluminescence degradation of InP/ZnSexS1-x/ZnS quantum dot films

InP/ZnSexS1-x/ZnS quantum dots (QDs) are promising candidates for next-generation electroluminescent devices. However, their photoluminescence (PL) irreversibly quenches over time under ambient conditions, limiting open-air manufacturing techniques such as inkjet printing. While most degradation studies have focused on QD dispersions rather than the QD films, critical for colour conversion, electroluminescent, and sensor devices, remain less understood. In this work, we investigated the PL quenching of InP/ZnSexS1-x/ZnS QD films by varying the film thickness, humidity level, and temperature. We find that higher relative humidity slows PL quenching, likely due to photoinduced fluorescence enhancement. Increasing QD film thickness from 19 nm to 100 nm extended the PL degradation half-life (τ1/2) by 5.6 times. Heating above 100 ◦C, under vacuum (0.1 mbar), accelerates degradation due to stripping of ligands and trap state formation from strain and atomic mobility. In-situ near-ambient X-ray photoelectron spectroscopy reveals oxidation products such as In₂O₃, InPOₓ, ZnO, SeO₂, and SO− x . Applying a 47-nm-thick polymethyl methacrylate barrier increases τ1/2 by 12-fold, significantly enhancing air stability. These findings provide insights into degradation mechanisms and strategies for improving the durability of QD films in practical applications.