Gaussian approximation of the spectral dependence of the absorption spectrum in polymer semiconductors

The optical and photoelectric properties of present-day photosensitive polymers are of particular interest due to their prospects for use in various photoelectric applications. Here the absorption edge is studied by the constant photocurrent method which is widely used for studies of inorganic materials. For the objects to be studied, PCDTBT and PTB$_7$ polymers and their mixtures with the PC$_{71}$BM fullerene derivative are chosen. The spectral dependences of the absorption coefficient for the pure polymers and mixtures are approximated on the assumption of the Gaussian distribution of the density of states in the bands of the components, which provides a means for estimating the electrical band gaps. In addition, such processing of the spectra makes it possible to confirm some important inferences about the states responsible for optical transitions in the low-energy absorption region.