Colloidal Perovskite Nanocrystal Superlattice Films with Simultaneous Polarized Emission and Orderly Electric Polarity via an In Situ Surface Cross-Linking Reaction

Superlattices (SLs) based on colloidal nanocrystals (NCs) represent a fascinating structure with long-range and ordered NCs inside the assembled superstructures, displaying great potential application in electronic devices because of the customizable arrangement of building blocks. It is a great challenge to achieve macroscopical SL films by a solution process due to the inherent sensitivity and difficulty in controlling colloidal NCs. In this study, we propose a controllable strategy to create perovskite CsPbBr₃ NC SL films through a surface in situ cross-linking reaction incorporating conjugated linoleic acid (CLA), a naturally polymerizable small molecule. CLA enables the in situ cross-linking of adjacent NCs under polarity-triggered conditions, which effectively arranges the NCs in a solid form at a molecular level to achieve fcc SL structural films. Importantly, we report for the first time NC SL films that are simultaneous with outstanding intrinsically linearly polarized emission and orderly electric polarity, which are derived from consistent dipole alignment, thus showing promising potential for application in information storage and optoelectronics. This method provides a general bottom-up approach, expanding the assembly library for fundamental studies and technological applications.