Cation Dependent Linear Dichroism in PL Spectra of Self-assembled Perovskite Nanoparticle Film and Nanoparticle-Liquid Crystal Mixtures

Abstract

Self-assembly films formed by perovskite nanoparticles (NPs) exhibit fascinating collective assembly phenomena, but the in-depth description is still lacking. Here, three perovskite APbBr₃ NPs, where A⁺ includes Cs⁺, MA⁺, and FA⁺, with similar size wrapping with various ligands, are used as model materials. The degree of linear polarization (DOLP) strongly depends on the aggregation of the NPs. All colloidal solutions exhibit non-polarized luminescence, whereas the DOLP of APbBr₃ films range from ~0% to 10%. This can be attributed to the dipole-dipole interaction resulting from lattice distortion, imperfect shape, as well as the ligand features. Accordingly, the dipole of a NP can also interact with the dipole of liquid crystal molecules, resulting in a centimeter-scale device comprising the mixture of NPs and liquid crystal with DOLP of 50%. Our work highlights the potentials of using dipole-dipole interaction to construct NPs into large-scale structures with controllable collective optical phenomena, particularly offering a new method for linearly polarized emission.