Dual‐State Emissive and Spectrally Tunable Carbazole Fluorene Copolymer Films for Agricultural Light Conversion

ABSTRACT

Agricultural light‐conversion films require luminophores that combine spectral selectivity, solid‐state emission, matrix compatibility, and operational stability. Building on our earlier carbazole/fluorene‐based light‐conversion system, this work redesigns the polymer structure by introducing benzene‐linked fluorene segments and varying the content of benzothiadiazole‐containing units, with the aim of improving the overlap between absorption and plant‐relevant spectral regions. Three dual‐state emissive (DSE) terpolymers, PFCz‐B10, PFCz‐B20, and PFCz‐B40, consisting of carbazole, fluorene, and benzothiadiazole‐containing phenyl units, were synthesized and blended with poly(methyl methacrylate) (PMMA) to form light‐conversion films. The benzothiadiazole content was varied from 10% to 40% to tune the spectral response. Spectroscopic, stability, and morphology analyses show that the films absorb strongly in the ultraviolet (UV) region and convert incident UV light into blue or red–orange emission while retaining high transmittance in the red–orange window. Among the series, PMMA@0.5PFCz‐B20 retained 95.8% of its initial absorbance after 6 h of UV irradiation, indicating the best photostability under the tested conditions. These results demonstrate that monomer‐level structural regulation is an effective route for tuning light‐conversion behavior and improving the spectral suitability of DSE polymer films for agricultural covering applications.