Polymer Cross‐Linking Strategy Enables High Performance and High Mechanical Stability Flexible Quasi‐2D Perovskite Light‐Emitting Diodes

Abstract Flexible perovskite light‐emitting diodes (f‐PeLEDs) have become one of the important candidates for lighting and display in wearable electronic devices due to their high flexibility and portability. However, the device performance of f‐PeLEDs is much lower than that of rigid devices, mainly due to the lack of mechanically stable perovskite films with good optoelectronic properties. In this work, a multifunctional strategy is proposed to obtain f‐PeLEDs with increased mechanical stability and optoelectronic performance. The polylactic acid (PLA) polymer with high flexibility is first incorporated into a quasi‐two‐dimensional (quasi‐2D) film, which undergoes in situ cross‐linking and forms a polymer cross‐linking network in a quasi‐2D film. Moreover, C═O functional groups in PLA can coordinate with unsaturated Pb²⁺ sites to efficiently passivate defects in perovskite films. The excellent flexibility of PLA and dynamic physical cross‐linking sites between PLA and the perovskite lattice enhance mechanical stability and still exhibit stable optical properties after repeated bending. Finally, the champion external quantum efficiency (EQE) of 15.94% is successfully implemented and maintains an initial EQE of over 60% after 10 000 bending cycles with a curvature radius of 3 mm. Therefore, the well‐designed cross‐linking strategy provides an efficient strategy for manufacturing stable f‐PeLEDs.