High-efficiency blue colloidal quantum dot light-emitting diodes enabled by zinc iodide ligand modification.

Quantum dot light-emitting diodes (QD-LEDs) have emerged as one of the most promising technologies for next-generation displays and solid-state lighting. However, the commercialization of full-color QD-LEDs is severely limited by the low efficiency and short lifetime of blue devices, mainly stemming from insufficient exciton radiative recombination caused by surface defect-induced carrier trapping and electron leakage from QDs to hole transport layers (HTLs). We introduce a surface modification strategy for QDs using inorganic ZnI2-derived iodide (I-) as a functional ligand to address these issues. The iodide (I-) effectively passivates QD surface defects, suppressing defect-assisted nonradiative recombination. More importantly, the electron-accepting nature of iodide induces a downward shift of QD energy levels, increasing the electron transport barrier from QDs to the HTL, thereby reducing electron leakage. Benefiting from this synergistic effect, the resulting blue QD-LEDs achieve a maximum external quantum efficiency (EQE) of 26.5%, ranking among the highest values reported for blue QD-LEDs emitting in the 450-480 nm range. Meanwhile, the device operational lifetime is extended two fold compared with the control devices. This work provides an effective strategy for realizing high-performance blue QD-LEDs and accelerates the commercialization of full-color QD-LED technology.