Surface Energy Modulation of NiOx through In Situ Click-Cross-Linked Networks for Air-Processed Flexible Blue
Xinhao Liu1, Jiandong Wu1, Huixin Li1
1State Key Laboratory of Solidification Processing, Center for Nano Energy Materials, School of Materials Science and Engineering, Northwestern Polytechnical University and Shaanxi Joint Laboratory of Graphene, Xi'an 710072, China.
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Air-processed flexible blue perovskite light-emitting diodes (PeLEDs) are crucial for advancing flexible displays and wearable optoelectronic devices. However, the NiOx 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 NiOx film and the interfacial contact between NiOx and perovskite. Furthermore, the polymer network precisely modulates the surface energy of the NiOx film based on the selective hydrogen bond interaction between the polymer and solvent molecules (H2O and DMSO). The flexible NiOx film is capable of simultaneously achieving good DMSO wetting and H2O 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.
