Universal exciton size scaling in π conjugated systems

The excited state properties of many oligomers or polymers are of particular importance as they are directly related to light absorption and emission as well as to photoconductivity, which govern most of their potential applications. Oligomers with a finite, well-defined chain length can serve as model systems for the investigation of general and fundamental properties of the whole material class. We show that the primary gap excitations in a number of such model systems are essentially delocalized over the entire molecules. The extension of the corresponding exciton scales with the molecule length only and is fully independent of the details of the corresponding molecular structure. (C) 2000 Elsevier Science B.V. All rights reserved.