Synthesis of WO_n-WX₂ (n=2.7, 2.9; X=S, Se) Heterostructures for Highly Efficient Green Quantum Dot Light-Emitting Diodes

Preparation of two-dimensional (2D) heterostructures is important not only fundamentally, but also technologically for applications in electronics and optoelectronics. Herein, we report a facile colloidal method for the synthesis of WO_n-WX₂ (n=2.7, 2.9; X=S, Se) heterostructures by sulfurization or selenization of WO_n nanomaterials. The WO_n-WX₂ heterostructures are composed of WO_2.9 nanoparticles (NPs) or WO_2.7 nanowires (NWs) grown together with single- or few-layer WX₂ nanosheets (NSs). As a proof-of-concept application, the WO_n-WX₂ heterostructures are used as the anode interfacial buffer layer for green quantum dot light-emitting diodes (QLEDs). The QLED prepared with WO_2.9 NP-WSe₂ NS heterostructures achieves external quantum efficiency (EQE) of 8.53 %. To our knowledge, this is the highest efficiency in the reported green QLEDs using inorganic materials as the hole injection layer.