This study aimed to prepare films based on the plant-derived materials galactomannan and quercetin, and characterize them using X-ray diffraction (XRD), Fourier-Transform Infrared Spectroscopy (FTIR), and Impedance Spectroscopy (IS). Galactomannan is a polysaccharide found in the endosperms of seeds from plants in the Fabaceae family, and quercetin is a flavonoid found in various vegetables, both of which are promising components in the research for the production of organic semiconductor devices. After extracting galactomannan (Gal) from the seeds of Adenanthera pavonina L. and quercetin (Q) from onions (Allium cepa L.), 2% galactomannan film was added 1% yellow onion extract. XRD was performed using an Empyrean diffractometer, scanning from 5º to 60º with an angular step of 0.02º/s and a count time of 2 s. FTIR was conducted using a Perkin Elmer Spectrum Two spectrometer in the range of 4000 to 600 cm−1, with a resolution of 4 cm−1 and 32 accumulations. IS measurements were obtained using an Agilent 4294 impedance analyzer, in the radiofrequency range between 100 Hz and 1 MHz. XRD analysis was performed on onion powder, while FTIR and IS analyses were conducted on the 1% GalQ film. The FTIR spectra showed typical bands of galactose, mannose and quercetin. The diffractograms did not reveal diffraction peaks associated with an organized crystalline structure, and the galactomannan and quercetin films exhibited dielectric behavior with the ability to store electrical energy. Quercetin altered the conductivity of galactomannan, enhancing the electrical properties for applications in the organic semiconductor industry.