Investigation on the wetting issues in solution processed quantum dot light-emitting diodes with inverted tandem structure

To protect the quantum-dots (QDs) from dissolving by the solvents of upper hole transporting layer (HTL) in inverted structure, we took a thorough study on the influence of HTL materials and solvents on the photoluminescence (PL) intensity of QDs. The experimental results confirm that the QDs layer can survive after solution processing by carefully selecting the suitable HTL material and the solvent. Second, after overall estimating the wetting enhancement ability and the additive residue of several different additives, IPA was selected as the additive to facilitate the deposition of a hydrophilic poly(ethylenedioxythiophene)/polystyrenesulfonate (PEDOT:PSS) hole injection layer (HIL) on top of hydrophobic HTL layer. Finally, to obtain efficient inverted tandem QLEDs, a solution-processable interconnecting layer (ICL) based on PEDOT/ZnO is developed. The proposed ICL and the developed fabrication methods allow for realization of efficient inverted tandem QLEDs for next generation display and lighting applications.