Optical bandgaps of π-conjugated organic materials at the polymer limit:: Experiment and theory

In this Review, the extreme care that must be taken when predicting the optical properties of conjugated polymers via the oligomer approach, and when comparing theoretical and experimental data, is illustrated. In the first part, conceptual strategies for the correct determination of optical transitions from experimental spectra and relevant extrapolation procedures at the polymer limit are introduced. The impact of conformational, substitution, solvent, and solid-state effects on the optical properties is discussed in light of experimental data reported for molecular backbones based on phenylene, phenylenevinylene, and thiophene repeat units. A comparison is then made between experimental results and those provided by standard quantum-chemical methods, to assess their reliability.