Reversible thermally-switchable chirality of circularly polarized luminescence in perovskite nanocrystals enabled by cholesteric liquid crystals

Circularly polarized (CP) luminescence provides an additional degree of freedom for emerging integrated photonic and communication technologies, yet reversible switching of its handedness remains challenging as it is fundamentally constrained by the need to reconfigure chiral emitters. Here, we break this limitation by introducing a thermally programmable photonic strategy that enables reversible switching of CP light (right or left) without modifying the emitters themselves. This is achieved through modular heterostructure integration of perovskite nanocrystals (PNCs) with bilayer cholesteric liquid crystals (CLCs) of opposite handedness, where the CLCs function as dynamic chiral photonic filters. The switching mechanism is governed by temperature-driven spectral translation of the CLC photonic bandgaps (PBGs), arising from the thermally induced variation of the helical pitch that shifts the Bragg reflection wavelength. As the PBGs sequentially resonate with the narrowband emission of PNCs, selective suppression of opposite circular polarizations occurs, leading to deterministic inversion of CP luminescence handedness. The system delivers a large g lum of up to 1.84 and reversible dissymmetry switching ( Δ g lum > 3.3, Δ g lum = ∣ g lum + ∣ + ∣ g lum − ∣ ) across the visible spectrum. This work establishes a general photonic strategy for thermally programmable CP light handedness and holds promise for applications in adaptive photonic systems, secure optical communication, and advanced information technologies.