Investigating the polarized emission of P3HT films and the role of GO in the interfacial layer

In this work, P3HT:PCBM films were deposited on PEDOT:PSS and PEDOT:PSS:GO buffer layers, aiming to evaluate the impact of graphene oxide (GO) on photophysical properties using emission ellipsometry (EE). The characterization, involving Ultraviolet-Visible Absorption Spectroscopy (UV-Vis), Photoluminescence Spectroscopy (PL), Photoluminescence Excitation Spectroscopy (PLE), and EE. Morphological characterization was made using Atomic Force Microscopy (AFM). It was observed that GO significantly enhances the optical measurements and improves its interaction with PCBM. Both showed the quenching effect, as observed in the PL measurement, and contributed to a more uniform energy transfer compared to the ITO/PEDOT:PSS/P3HT, as demonstrated in the EE measurements. Raman analysis confirmed structural changes and variations in $\pi$-conjugation, with I_b/I_a ratios indicating partial preservation of molecular order in GO films. EE provided detailed polarization-resolved emission parameters; GO-containing films exhibited enhanced linear polarization (S₁/S₀) and increased circularly polarized components (S₃/S₀), suggesting improved interchain interactions and charge transfer. These effects were most evident in the combined GO and PCBM system, indicating that GO, even when restricted to the buffer layer, significantly improved the properties of the active layer.