High-performance all-solution-processed inverted quantum dot light-emitting diodes enabled by water treatment

All-solution-processed inverted quantum dot(QD)light-emitting diodes(QLEDs)with transparent bottom cathodes can be directly connected to the n-type thin-film transistors,offering a feasible solution for low-cost active matrix-driven QD displays.However,the subsequent solution-deposition of the hole-transporting layer destroys the underneath QD films,resulting in largely deteriorated device performance.Various strategies have been implemented to prevent QD film from dissolution,but all at a heavy cost of device performance suffering from either reduced efficiency or increased driving voltage.Here,a facile and effective water-treatment approach for QD film to fabricate inverted QLEDs through all solution processing is reported.The water treatment substitutes the long-chain oleate ligands with hydroxyl groups,resulting in significantly improved non-polar solvent resistance of the QD films.Importantly,the QD films reserve their excellent photoluminescence efficiency after water treatment.With the water-treated QD film as the emissive layer,all-solution-processed inverted red QLED with a peak external quantum efficiency of 19.6%,a turn-on voltage of 1.8 V,and a T50 operational lifetime of 150,000 h at 100 cd·m^(-2) was achieved.Furthermore,efficient and low-voltage-driven green and blue QLEDs can also be prepared with this method.This work provides a feasible strategy for the fabrication of high-performance all-solution-processed inverted QLEDs,paving the way toward achieving QLEDs by all ink-jet printing.