<b>Over 20% external quantum efficiency in near-infrared quantum dot light-emitting diodes by using photo-crosslinked hole-transport layers</b>

Visible quantum dot light-emitting diodes (QD-LEDs) have satisfied the requirements for commercial displays. However, the performance of near-infrared (NIR) QD-LEDs lags considerably behind, due to the comparatively inferior quality of NIR QDs and the current limitations on device architecture suitable for NIR electroluminescence. Here, we present an efficient and reproducable “full-process defects etching” strategy of using inorganic fluorides as key additives to completely suppress surface oxidizing agents on QDs throughout the synthesis and to minutely control QD growth, producing heavy-metal-free, highly regular InAs/InP/ZnSe/ZnS QDs with near 100% quantum yields. Moreover, we developed an approach of <i>in-situ</i> photo-crosslinking blended hole-transport materials for accurate modulation of energy levels of hole-transport layers (HTLs). The crosslinked HTLs substantially enhance hole transfer to the emitting layer for balanced carrier dynamics in QD-LEDs. The resulting NIR QD-LEDs exhibit a peak external quantum efficiency of 20.5%, a high radiance of 581.4 W sr⁻¹ m⁻² and an ultralong half-lifetime of 550 h at 50 W sr⁻¹ m⁻², making the device the best-performing solution-processed NIR QD-LEDs to date. This study represents a significant step towards practical application of NIR QD-LEDs.