Abstract: This work was focused on the study of electrical conductivity to the combination of Polythiophene (PT) thin film and Chlorophyll (CHLO) thin film by layered on Indium Tin Oxide (ITO) substrate as p-n heterojunction solar cell. PT thin film is deposited to the ITO substrate by using electrochemistry method. CHLO thin film is coated on PT thin film by using the spin coating method. Current and voltage of ITO/PT/CHLO thin film are measured in the dark and under different light intensity by using the four point probes. The results showed that PT thin film was successfully coated with CHLO on ITO substrate with different thicknesses. Electrical conductivity in the dark showed an increasing with the increasing of PT thin film thickness. While with the increasing of CHLO thin film thickness, electrical conductivity in the dark is consecutively changed. Electrical conductivity under different intensity of light increased with the increasing of light intensity. Electrical conductiv...