Highly efficient and bright green quantum‐rod light‐emitting diodes with eliminated charge leakage

Abstract The external quantum efficiency (EQE) of QLEDs reaches a theoretical limit of about 25%, primarily constrained by light outcoupling efficiency ( ƞ out ). In contrast, quantum rods (QRs) provide directional light emissions that can exceed the ƞ out limitations of spherical QDs, potentially double the EQE of LEDs. However, developing high‐efficiency QRLEDs faces several challenges, such as low quantum yield of the QRs and charge imbalance in the device. Recent advancements in QRLEDs have achieved an EQE of 22%, and the study focuses on red QRs only. Expanding QRLEDs for full‐color displays is essential for producing highly efficient green QRs. In this work, we synthesized highly efficient green CdSe/Cd x Zn 1‐x S QRs at an emission wavelength of 518 nm, achieving a quantum yield of over 95%. We identified two pathways of electron leakage in QRLEDs at the organic/inorganic interface, ultimately limiting the device's efficiency. We improved the device efficiency by mitigating electron leakage and enhancing hole injection in QRLEDs using multi‐stacked HTLs. As a result, QRLEDs achieved record‐breaking performance metrics: an EQE of 19.4%, a current efficiency of 72 cd/A, and a luminance of 320,000 cd/m 2 .