In Situ Fabrication of Lead-Free Cs3Cu2I5 Nanostructures Embedded in Poly(Vinylidene Fluoride) Electrospun Fibers for Polarized Emission

Polarized emissive materials with anisotropic nanostructures have attracted tremendous attention as potential substitutes for polarizers. Herein, the electrospinning technique is adopted to realize in situ fabrication of lead-free halide Cs3Cu2I5 nanostructures embedded in poly(vinylidene fluoride) (PVDF) micro/ nanofiber films for polarized luminescence generation, with a photoluminescence quantum yield (PLQY) of 33.3-86.1%. The functionality of the polymer PVDF as a protector and its interactions with Cs3Cu2I5 were demonstrated. The Cs3Cu2I5/PVDF composite nanofibers exhibit a higher degree of PL polarization ratio (P) than that of composite microfibers, reaching a highest P of 0.4 and long-term stability. This polarized emission is attributed to the directional transition dipole moment (TDM) induced by the asymmetric crystal structure of aligned Cs3Cu2I5 nanorods and dielectric confinement effect of the PVDF matrix. The universality of the in situ electrospinning preparation strategy is confirmed by the fabrication of a Cs3Cu2I5/PVA fiber film with a P of 0.5. The reported Cs3Cu2I5/polymer nanofiber films with bright and highly polarized light emissions will have great potential for optoelectronic applications such as liquid crystal display (LCD) backlighting, spectrum splitting, waveguides, lasers, and polarized photodetectors.