OPTICAL-RESPONSE OF CONJUGATED POLYMERS

We present a simple model for the description of the linear and nonlinear optical response of conjugated polymers, where the pi electrons are confined in a periodic system composed of anharmonic potential wells. We calculate the optical band gap, the polarizability, and the second hyperpolarizability as a function of the molecular length for the oligomers of thiophene and benzene, adjusting the model parameters to two band-gap measurements. We find them to be in fair agreement with experimental data. Furthermore, the length dependencies are discussed and compared with experimental and theoretical reported values. The model is very suitable for studying the sensitivity of the optical response to conformational disorder.