Novel method doped carbon with nanoparticle Cr2O3 and thin film has been studied in much thought in wavelength range, the doping can help new excellent physical and chemical properties for carbon, this application has a semiconductor feature. Nanocomposite thin film deposited on copper and glass substrates have been created by utilizing Spray Pyrolysis method. The precursor solution for the nanocomposite (Cr2O3/C) was blended with the polyethylene glycol as a colloidal. The optical band gap is a crucial property for the nanocomposite, for instance, nanocomposite thin film of Cr2O3/C was kept by shower process on glass and copper substrates. The band gap for the nanocomposite photo-catalytic has been finished using X-ray diffraction, UV-Vis spectrometer. The assessed optical band gaps for direct and indirect transition values determined and were 3. 5, 3. 25 eV and photon energy 1. 65 eV to carbon doped by nanoparticle Cr2O3. Thin film thickness ranging between 45-160 μ m This paper achieved the doped carbon by nanoparticles of Cr2O3 for thin layer coating in flat plate collector. New coating activity may be given by novel nanocomposite Cr2O3/C structure as a semiconductor. Results showed a new nanocomposite to enhance the absorption of the solar energy light activity. Prog. Color Colorants Coat. 13 (2020), 143-154© Institute for Color Science and Technology.