Fig. 3: Spectroscopic analysis of BPEs.

a Optical microscope images of the oxidized (left) and reduced (right) PEDOT:SDS regions where Raman spectra were acquired. b Structural differences between the benzoid and quinoid forms of PEDOT, with arrows indicating the differences in the bonds of Cα and Cβ atoms in the thiophene ring. c Raman spectra of the oxidized (light blue) and reduced (dark blue) PEDOT:SDS regions. The gray shading highlights the main peak at 1422 cm⁻¹ (Cα=Cβ symmetric), and the red shading shows a shoulder at 1553 cm⁻¹ (Cα=Cβ asymmetric). Inset: details of the main peak region. d X-ray photoelectron spectroscopy (XPS) spectra of oxidized (left column) and reduced (right column) PEDOT:SDS regions, respectively. Spectra include the C 1s (i and ii), O 1s (iii and iv), and S 2p (v and vi) regions for each sample.