A Spiro‐Type Self‐Assembled Hole Injection Layer for High‐Performance Quantum‐Dot Light‐Emitting Diodes

ABSTRACT Poly(3,4‐ethylenedioxythiophene): poly(styrene sulfonate) (PEDOT:PSS) is widely used as a hole injection layer (HIL) in quantum‐dot (QD) light‐emitting diodes (LEDs). However, its acidic and hygroscopic nature erodes the indium tin oxide electrode, causing serious device stability issues. To overcome the limitations, QLEDs that utilize self‐assembled monolayers (SAMs) as the HILs have been proposed and demonstrated, offering both high efficiency and improved stability. The D1 SAM forms a high‐quality film characterized by excellent transmittance and low surface roughness. Crucially, it possesses a high work function, which facilitates effective hole injection into the QD film, thereby improving charge balance and reducing the accumulation of excess charges within the QLED. As a result, the D1‐based red QLED exhibits a maximum external quantum efficiency of 26.6%, a high brightness of 240 500 cd m −2 at a voltage of 8 V, significantly outperforming the device based on PEDOT:PSS. This SAM HIL approach paves the way toward commercially viable, high‐performance QLEDs in next‐generation displays.