Efficient Quantum Dot Light-Emitting Diodes Based on Solution-Processed WOx Nanoparticles

Transition metal oxides, represented by tungsten oxides (WO_x), are considered as a potential candidate of hole injection materials for optoelectronic thin-film devices to overcome the acidity and hygroscopicity of PEDOT:PSS. However, due to the lack of in-depth study of materials and careful construction of film interfaces, the performance of as-prepared quantum dot light-emitting diodes (QLEDs) is generally not ideal, which limits the further development and research of this field. Here, solution-processable WO_x nanoparticles (WO_x NPs) with excellent film-forming properties are synthesized and introduced to solve this issue. Meanwhile, in situ photo-induced ligand exchange enabled the robust interfaces of WO_x films, expanding the selection of functional materials. The as-prepared QLED devices achieved a peak external quantum efficiency (EQE) of 15.09%, representing one of the best performances for WO_x-based QLEDs. Furthermore, high-resolution WO_x patterns (pixel size: ≈700 nm) through regional exposure were developed successfully, demonstrating the potential in future high-resolution and high-performance displays, and laying the foundation for the implementation of all inorganic QLEDs.