Optical and Dielectric Characteristics of Photoactive Layer Thin Films for Organic Photovoltaic Cells

Abstract

The thin films of poly[2-methoxy-5-(2'-ethylhexyloxy)-1,4-phenylenevinylene] (MEH- PPV) used as photoactive layer in organic photovoltaic cells were prepared on glass substrates by the spin-coating technique. The transmittance spectra of thin films were measured by a double beam spectrophotometer. The optical constants such as refractive index and extinction coefficient of the thin films were determined from the measured transmittance spectra using the method of whole optical spectrum fitting. The complex dielectric constant and the complex optical conductivity of the thin films were obtained. In addition, the optical bandgap of the thin film were calculated according to the Tauc's law. The results show that the thin films exhibit direct allowed transitions and the optical bandgap is about 2.18 eV. These results provide some useful references for the design and optimization of device structure in organic photovoltaic cells.