Thickness, t ± 5 (nm) Highlights Plasma polymerized 2-furaldehyde thin films of different thicknesses were deposited onto glass substrate in optimum conditions by glow discharge reactor. XRD results confirmed the amorphous nature of the films. The as-deposited PPFDH thin films contain asymmetric C-H and C≡C stretching bonds due to plasma polymerization. The direct and indirect optical band gaps of the PPFDH thin films of different thicknesses were found to be 3.40-3.45 and 2.10-2.45 eV, respectively. The dispersion energy increases from 6.35 to 18.85 eV while oscillator energy decreases from 3.17 to 2.83 eV with increasing thickness of the thin films.