Amplified Photoluminescence of CsPbX₃ Perovskites Confined in Silica Film with a Chiral Nematic Structure

Abstract Metal halide perovskites (MHPs, CsPbX3: X = Cl, Br, I) have advanced the field of optoelectronic devices due to their remarkable light‐emitting capabilities, stemming from the large overlap between their emission and absorption spectra, offering the possibility to reabsorb their own emitted photons. Herein, a straightforward method is reported to confine CsPbBr₃ into mesoporous silica films with a chiral nematic structure, allowing the amplification of the photoluminescence (PL). The simple room temperature ligand‐free synthesis allows facile growth of CsPbBr₃ in silica photonic films, in which the Bragg peak position can be tuned from the UV to the visible range. The perovskite/silica films demonstrate a remarkable improvement in PL intensity and lifetime compared to the as‐synthesized non‐confined perovskite nanocrystals (NCs) due to the overlap of the Bragg peak position of the chiral nematic photonic films and CsPbBr₃ absorption band. Such a PL enhancement stems from the slow photon effect induced at blue and red Bragg peak edges that facilitates the photon recycling of the emitted photons. This innovative approach offers a new way to fabricate highly emissive and long‐lived photoluminescent films at ambient conditions, potentially advancing perovskite utilization in light‐emitting devices.