Tuning Superradiance and Emissive States in Anthracene Thin Films with Temperature

Superradiance and the emergence of longer-lived, lower-energy emissive species in anthracene thin films are investigated to elucidate the complex photophysical behavior of polycyclic aromatic hydrocarbons (PAHs) relevant to optoelectronic applications. Employing steady-state and time-resolved spectroscopy, complemented by temperature-dependent powder X-ray diffraction (PXRD), we probe the temperature-dependent excited-state dynamics of anthracene thin films. At reduced temperatures, enhanced 0–0 emission and accelerated monomer emission decays are observed, consistent with superradiance arising from increased exciton delocalization within J-aggregates. Time-resolved emission spectral analysis reveals a long-lived, red-shifted emissive state persisting up to ∼200 ns, with isoemissive points at ∼455 nm and ∼480 nm at both 77 and 150 K, indicating dynamic interconversion between multiple emissive species. At room temperature, only a single isoemissive point at ∼455 nm is observed, suggesting a dominant emissive species. PXRD analysis indicates increased microstrain and subtle structural rearrangements at lower temperatures, which may facilitate the formation of excimer states or other low-energy configurations. The interplay of superradiance, excimer formation, and potential contributions from localized states or shallow traps underscores the intricate relationship between molecular structure, temperature, and emission dynamics in anthracene thin films, offering insights into the design of advanced organic optoelectronic materials.