Operational Stability Enhancement of Pure‐Blue Perovskite Light‐Emitting Diode With AgCuGaS ₂ Quantum Dot Solids as Hole Transport Layer

Quasi‐two‐dimensional (quasi‐2D) Ruddlesden‐Popper (RP) perovskites characterized by self‐assembled multiple‐quantum‐well structures are promising emitters for high‐resolution displays. However, the stabilities of blue perovskite light‐emitting diodes (PeLED) are major hurdles toward full‐color applications. Here, we introduce wide‐gap, high‐mobility silver‐copper‐gallium‐disulfide (AgCuGaS 2 , ACGS) quantum dot (QD) solids as novel hole transport layer (HTL) to address the bottlenecks of the short lifetime of blue PeLEDs through controllable charge transport. ACGS QD solids provide enhanced hole transport through adaptable band structure and high hole mobility of 0.191 cm 2 V −1 s −1 . In addition, Zn 2+ attached to surface of the ACGS QD, stabilize the halide anions through ionic interaction, thus suppressing ion segregation and lattice defect formation in quasi‐2D perovskite. The resulting pure‐blue PeLEDs (471 nm) based on ACGS QD solids achieve a maximum EQE of 6.92% and a record operating lifetime with T 50 (luminance drop to half of the initial value) of 78 min at 100 cd/m 2 , significantly higher than controlled devices based on organic HTL materials (18 min).