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_xZn_1-xS 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/m².