One-dimensional CsPbBr₃ superlattices with polarized and amplified spontaneous circularly polarized emissions

Nanocrystal superlattices typically occur in two- or three-dimensional configurations, constrained to the micrometer scale and with limited size tunability. Here, we report one-dimensional superlattices prepared by self-assembly of CsPbBr₃ nanorods and nanoplatelets. These exhibit a hierarchical structure, evolving from ribbons (µm) of nanorods or nanoplatelets to assemblies of ribbons (mm). These superlattices have a diameter of 0.8-1 µm and length in the range of 13-1500 µm, and their aspect ratio can be tuned from 14 to 1200 by adjusting the shape of the nanorods and nanoplatelets. Thanks to their anisotropic structure, the superlattices show strong polarized emission with a near-unity degree of polarization, ≈4 times larger than that of randomly assembled film. These superlattices also exhibit chiral optical response (circular dichroism and circularly polarized emission). Since no chiral ligands are used in the synthesis, the chiral signal (negative or positive) from the superlattices is random. However, the signal can be controlled after the addition of chiral ligands. The maximum dissymmetry factor of the luminescence (g_lum) is -0.11, and can be further amplified to -0.32 in the amplified spontaneous emission of the superlattices.