Local Symmetry Breaking Facilitates Near-Infrared Circularly Polarized Lanthanide Emission in Perovskite Nanocrystals

Imparting chiroptical activity of lanthanide transitions provides an attractive route to circularly polarized luminescence. However, obtaining intense emission from their Laporte-forbidden f–f transitions while also generating significant rotatory strength remains a formidable challenge in materials design. This work establishes a platform for efficient near-infrared (NIR) circularly polarized luminescence (CPL), centered on the telecom-relevant C-band around 1550 nm, from lanthanide dopants (Yb3+/Er3+) embedded in chiral perovskite nanocrystal (CsPbX3) hosts. Atomic-scale structural analyses reveal a preferential enrichment of lanthanide concentration near the nanocrystal surfaces, where chiral ligands distort the lattice, lowering the local symmetry. Spectroscopic measurements confirm the highly efficient host-to-dopant energy transfer, facilitating strong CPL, with a luminescence dissymmetry factor (glum) of 0.36 and a CPL brightness (BCPL) of 4.2 × 105 M–1 cm–1 at 1550 nm, representing nearly four orders of magnitude above the previous benchmark. With improved photostability, these results establish lanthanide-doped chiral perovskite nanocrystals as a promising route to telecom-relevant CPL.