We present results of an X-ray photoelectron spectroscopy (XPS) study of the interfaces between polypyridine (PPy) and model sulfonic acid containing polymer and molecule. We show that the N 1s level splits reflecting protonation of a substantial fraction of the PPy N sites. Density functional theory (DFT) is employed to compare excitation energies, bond angles, highest occupied molecular orbital (HOMO), lowest unoccupied molecular orbital (LUMO), and density of states of oligomers of pyridine and protonated pyridine. These results are in accord with the proposed origin of the red shift of the emitted light under forward bias in color-variable alternating-current light emitting (SCALE) devices.