Theory of photoexcitations in conjugated polymers: The effects of Coulomb interactions

Abstract

Many-body Coulomb interactions make understanding the complete excitation spectra of conjugated polymers a formidable task, and a variety of sophisticated experimental and theoretical techniques have been used in an attempt to elucidate their complicated electronic structure. It is thus crucial to have a intuitive, physical picture in order to interpret the wide range of available experimental data. We present the results of calculations within an exciton basis which allows for a simple pictorial description of all linear and nonlinear excitations in conjugated polymers, and settles a number of longstanding controversies. The exciton basis further allows us to justify the application of single configuration interaction (SCI) techniques to the understanding of nonlinear optical experiments in the low energy region. We show that SCI can give a clear, self-consistent picture of the photoexcitations in poly(para-phenylene vinylene), a conjugated polymer which has attracted much recent interest.