Low Efficiency Roll‐Off and High Current Efficiency Light‐Emitting Diode Enabled by Graded CdSe/ZnSe/ZnS Colloidal Quantum Wells

ABSTRACT Colloidal quantum well light‐emitting diodes (CQW‐LEDs) hold tremendous potential for next‐generation display and lighting applications, owing to their high color purity, excellent efficiency, and low fabrication cost. However, efficiency roll‐off at high current density makes it challenging to achieve high brightness and long lifetime. Here, we designed CdSe/ZnSe/ZnS core/shell/shell CQWs with near‐unity photoluminescence quantum yield. The graded heterostructure promotes carrier injection, and the bottom‐emission device based on CdSe/ZnSe/ZnS CQWs exhibits remarkably suppressed efficiency roll‐off with a record‐high J 90 (current density for EQE to decrease to 90%) of 485 mA/cm 2 and a long operational lifetime (T 95 @ 100 cd/m 2 ) over 47000 h. In addition, the top‐emission device also shows low efficiency roll‐off and high current efficiency of 36.5 cd/A. This study provides a compositionally graded approach to suppress efficiency roll‐off in CQW‐LEDs, demonstrating the strong potential of the newly developed CQWs for next‐generation ultrabright and highly efficient optoelectronic devices.