STUDY OF OPTICAL PROPERTIES OF CONJUGATED OLIGO-PHENYLEMIN-TYPE COMPOSITE FILMS WITH APPLICATIONS IN ORGANIC SOLAR CELLS

The study of the optical properties of films of oligo-phenyleneimine-conjugated (OIC) type compounds obtained by the mechanosynthesis route is reported. This process was carried out in a high energy mill in the absence of solvents and catalysts for a period of 90 minutes. Once the compound was obtained in solid state, different solvents were added to obtain a solution for deposition on substrates. The result of these deposits were thin films on glass substrates that were achieved by means of the spin coating technique, by means of this process film thicknesses between 100 and 150 nm were obtained. Transmittance T(%) measurements were performed in the range of 120 to 1100 nm and the absorption coefficient ? (h?) was calculated as a function of photon energy. The amorphous behavior of the material allowed to perform the study considering an exponential decay with tails in the density of states distribution (DOS); to calculate parameters such as the defect absorption coefficient ?D(h?), the UrbachEU energy and the band gap of the material or optical gap Eg. The data for the thin films fabricated with the mixture of OIC and different solvents were discussed and it was found that the best film with possible applications in solar cells was using tetrahydrofuran as solvent reporting an Urbach energy of EU= 0.2eV and an optical gap of Eu=2.7 eV.