Electron-Beam Cross-Linked Ligands Enable Highly Stable and Freestanding Perovskite Nanocrystal Films

Lead halide perovskite nanocrystals (PNCs) exhibit outstanding optical and electronic properties for next-generation optoelectronics; however, their instability under ambient conditions severely hinders their practical implementation. Here, we demonstrate a versatile ligand cross-linking approach via electron-beam irradiation that effectively enhances nanocrystal stability without compromising their exceptional optical properties. Electron-beam exposure induces cross-linking reactions within the native oleylamine and oleic acid ligand shell, forming a robust, interconnected organic network that substantially increases hydrophobicity, long-term ambient stability, and resistance to various solvents. Unlike polymer or micelle encapsulation strategies, our cross-linking method preserves the structural integrity of the PNC layer and its optical properties without introducing additional layers or barriers that could impede charge transport. We further exploit this technique to create unprecedented heterostructures, achieving dual-emission spectra without ion exchange. Additionally, we present a novel method for producing mechanically stable, freestanding PNC films, which significantly simplifies device fabrication. These findings open up new avenues for integrating highly stable perovskite nanocrystal layers into commercial-scale photovoltaic and optoelectronic devices.