Giant Shell Nanorods for High‐Efficiency and Low‐Roll‐Off Light‐Emitting Diodes

Abstract 1D colloidal semiconductor nanorods (NRs) offer polarized emission and enhanced photon out‐coupling efficiency for high‐efficiency light‐emitting diodes (LEDs). However, their practical application has been limited by severe efficiency roll‐off at high current densities due to thin radial shells along the radial direction and the high aspect ratio that leads to random orientation during the fabrication of solution‐processed films, which causes structural gaps, triggering leakage currents and ultimately exacerbating efficiency roll‐off. Here, fatty acid is introduced to mitigate the c ‐axial growth induced by phosphonic acid in traditional NRs synthesis, while promoting radial shell growth, thereby forming giant‐shell CdSe/CdZnSe/CdS/CdZnS NRs with an aspect ratio of ≈2.2. This design effectively alleviates electron leakage caused by random orientation in NR films, while minimizing interfacial defects and Auger recombination, achieving a near‐unity PLQY. Consequently, NR‐LEDs based on these NRs exhibit a peak external quantum efficiency (EQE) of 23.4% and a luminance of 289 000 cd m − 2 . Significantly, this NR design greatly suppresses the EQE roll‐off at high current density. Furthermore, the devices have a long T 95 lifetime of more than 10 000 h at a luminance of 1 000 cd m − 2 . This material design strategy lays the foundation for realizing highly polarized NR‐LEDs for efficient high‐definition displays.