Impact of morphology and composition of graphene aerosol–gel particles in thin films on ultrafast carrier dynamics studied via transient absorption spectroscopy

Carrier dynamics of a series of printed thin films made of graphene aerosol–gel inks with varying oxygen (with respect to carbon in the lattice) content were investigated via ultrafast pump–probe spectroscopy. This study builds upon previously reported work which compares printed graphene aerosol–gel films to pristine graphene films with atomically flat flake physical structure. The present study thus further investigates the tunability of graphene aerosol–gel films and presents a systematic extension using oxygen as the tuning element. We report on the transient change in the transmission (ΔT/T) of printed inks with various oxygen content spanning the visible to near-IR spectral range (3–0.8 eV). The transient electronic behavior is correlated with composition, shape and morphology of ink particles, and sp2 carbon quality. We demonstrate that higher oxygen content directly correlates with increased concentration of long-lived trapped electronic states. Based on density functional theory calculations, these trapped states may be attributed to the presence of substitutional oxygen.