Quasi‐2D Chiral Perovskite Janus‐Structural Nanofiber Film With Tunable Spectrum and Energy‐Transfer‐Amplified Circularly Polarized Luminescence

ABSTRACT Chiral metal halide perovskites hold great potential as circularly polarized luminescent (CPL) materials owing to their exceptional optoelectronic properties. However, chirality‐induced lattice distortions in intrinsically chiral systems often reduce photoluminescence (PL) efficiency, making it challenging to balance chirality and emission performance. In this study, we present a general strategy enabling efficient energy transfer (ET) from chiral quasi‐two‐dimensional (quasi‐2D) perovskite nanosheets to achiral perovskite nanocrystals or dye molecules, achieving extended fluorescence lifetimes and enhanced CPL activity in achiral hosts. We establish a direct correlation between ET efficiency and chiral amplification in quasi‐2D chiral perovskite/achiral perovskite composites. The Janus‐type heterostructures exhibit remarkable ET efficiency and pronounced chiral amplification, leading to a fourfold increase in the photoluminescence quantum yield of achiral components and a luminescence dissymmetry factor ( g lum ) value of 4.32 × 10 −3 , representing a 50% enhancement compared to pristine chiral perovskites. This design can be extended to achieve full‐spectrum, white‐light CPL emission. The optimized Janus composites show excellent environmental stability, highlighting their practical applicability. Overall, this work establishes a versatile platform for developing high‐efficiency, spectrally tunable, and integrated CPL light sources, providing new opportunities for advanced chiroptoelectronic applications.