22.8%‐EQE and ns‐Level Response CsPbBr ₃ Perovskite Quantum Dot‐Based Light‐Emitting Diodes

ABSTRACT Fast‐responsive and efficient perovskite QD‐based light‐emitting diodes (QLEDs) demonstrate significant potential in high refresh rate display applications. However, the response time and external quantum efficiency (EQE) remain limited by imperfect device architectures, including low carrier mobility in transport layers and severe interface losses. Here, we utilized a molecule (3‐(6‐(3‐(4,6‐di([1,1′‐biphenyl]‐4‐yl)‐1,3,5‐triazin‐2‐yl)phenyl)pyridin‐2‐yl)phenyl) diphenylphosphine oxide (ETL‐PO) as an electron transport layer (ETL) due to its high electron mobility, which could also reduce defects at the interface between the QDs and ETL in the perovskite QLED. The P═O group of ETL‐PO coordinates with undercoordinated Pb 2+ to suppress nonradiative interfacial recombination, while the conjugated backbone supports efficient electron transport and reduces the device's resistance and capacitance. Resultantly, the QLEDs based on ETL‐PO exhibit a total response time of 564 ns at an active area of 0.01 mm 2 , which is more than 50 times faster than that of 29 µs for control devices. Furthermore, a peak EQE of 22.8% with a maximum luminance of 105518 cd m −2 is reached. This work shows a perovskite QLED device successfully achieved both high EQE and nanosecond‐level response time, providing a new perspective for the field of optical communication and data transmission.