Surface Energy Modulation of NiO(x) through In Situ Click-Cross-Linked Networks for Air-Processed Flexible Blue Perovskite Light-Emitting Diodes.

Air-processed flexible blue perovskite light-emitting diodes (PeLEDs) are crucial for advancing flexible displays and wearable optoelectronic devices. However, the NiO functional layer in such a flexible device faces a critical challenge of surface energy control within an extremely narrow polarity range to balance water resistance and perovskite precursor wettability. Herein, we demonstrate the postpolymerization modification strategy of click-cross-linking that in situ constructs polymer networks, which significantly improves the mechanical flexibility of the NiO film and the interfacial contact between NiO and perovskite. Furthermore, the polymer network precisely modulates the surface energy of the NiO film based on the selective hydrogen bond interaction between the polymer and solvent molecules (HO and DMSO). The flexible NiO film is capable of simultaneously achieving good DMSO wetting and HO resistance, which facilitates the perovskite film fabrication under ambient conditions. Consequently, we realize the first air-processed flexible blue PeLEDs, achieving a peak external quantum efficiency (EQE) of 1.32% with exceptional bending durability, retaining over 80% of the initial EQE after 2000 bending cycles. This work offers a guideline for surface energy modulation to achieve a robust flexible inorganic hole transport layer for air-processed blue perovskite fabrication, opening an avenue for advancing flexible perovskite displays.