Efficient and Stable Flexible PeLEDs Enabled by Polymer Interfacial Permeation Engineering

ABSTRACT Flexible perovskite light‐emitting diodes (f‐PeLEDs) hold great promise for next‐generation optoelectronics, but their efficiency and operational half‐lifetime ( T 50 ) remain limited by poor film quality on deformable substrates. Herein, we develop a polymer interfacial permeation strategy by incorporating poly(2‐ethyl‐2‐oxazoline) (PEOXA) into the hole transport layer (HTL). Through an antisolvent‐free one‐step spin‐coating process, PEOXA spontaneously partitions between the HTL and perovskite emitting layer, forming a 3D interpenetrating network that simultaneously passivates defects and enhances mechanical flexibility. The carbonyl groups in the polymer chains act as Lewis bases, simultaneously improving luminescence efficiency and enhancing crystallinity. Meanwhile, the polymer incorporation reduces the Young's modulus, significantly boosting device flexibility. These synergistic effects enable green f‐PeLEDs to achieve a record‐high peak external quantum efficiency of 23.4% along with a power conversion efficiency of 26.7%, and demonstrate exceptional operational stability, with a measured T 95 lifetime of 3.2 h at an initial luminance of 1000 cd/m 2 . This work thereby establishes a versatile and robust strategy for the development of high‐performance, flexible perovskite optoelectronics.