Effect of an ultrathin molybdenum trioxide interlayer on the performance of inverted quantum dot light-emitting diodes

Quantum dots are a promising new candidate for use as emissive materials in the next generation of light-emitting diodes for lighting and display applications. One of the key issues in the solution preparation of inverted quantum dot light-emitting diodes (QDLEDs) is making a suitable sandwich structure of hydrophilic and hydrophobic layers. We solved this problem by inserting an ultrathin film of thermally evaporated MoO₃ between a hydrophilic PEDOT:PSS layer and a hydrophobic PVK layer by controlling the delicate process. Inverted QD LEDs with an optimal MoO₃ thickness of 5 nm exhibited a maximum current efficiency of nearly 4 cd A⁻¹, a maximum EQE of 2.7682%, and a maximum luminance of 9317 cd m⁻². Furthermore, the MoO₃ interlayer extends the lifetime of the QDLED devices to approximately 300%.