V₂O₅-Based Dual-Hole-Injection Layers Toward Efficient and Stable Quantum Dot Light-Emitting Diodes

Quantum dot light-emitting diodes (QLEDs) are one of the promising candidates for next-generation displays due to their outstanding color purity and tunability, device efficiency, and solution-processing compatibility. However, the commonly used hole injection layer (HIL) of polyethylene dioxythiophene:polystyrene sulfonate (PEDOT:PSS) raises concerns about inferior device stability and efficiency due to acidic and hygroscopic nature and unsatisfactory energy barriers. Here, we proposed a simple and universal HIL design strategy to achieve efficient and stable QLEDs by using vanadium oxide V2O5-based dual HILs. The V2O5 film facilitates hole-selective contacts by establishing ohmic-like interfaces and acting as a blocker to prevent back transfer, achieving a more efficient hole injection pathway through staircase energy-level alignment of the HILs. Additionally, it prevents acidic PEDOT:PSS from etching indium tin oxide (ITO) anode and improves its surface smoothness, enhancing the stability of QLEDs. Our HIL design strategy—V2O5/PEDOT:PSS dual HIL-shows its performance enhancement capacity for all red, green, and blue QLEDs with peak external quantum efficiencies (EQEs) of 23.56%, 12.35%, and 7.15% and corresponding lifetimes (T
$_{{95}}$
) at 1000 cd/m2 are 5630, 280, and 9 h, respectively (around eight-fold greater than those of solely PEDOT:PSS HIL-based QLEDs). Furthermore, the V2O5-based dual-HILs can be extended to inorganic/inorganic HILs from V2O5/PEDOT:PSS (inorganic/organic) HILs, where V2O5/MoOx HILs demonstrate similar performance enhancement capacity for all red, green, and blue QLEDs in device efficiency and lifetime. Our V2O5-based dual-HILs are expected to offer a simple and practical way to achieve a long lifetime while maintaining the efficiency of QLEDs.