Strongly confined polaron excitations in charged organic semiconductors

The performance of organic devices such as organic light-emitting diodes or organic field-effect transistors is intimately connected to the nature and dynamics of the charge carriers in the device components. Using the model oligomer octithiophene, we experimentally demonstrate that the low-lying electronic excitations in p-type doped films are significantly confined on the molecule due to polaronic effects and thus deserve the name polaron excitations. Our results allow for a quantitative experimental determination of the charge carrier (polaron) extension, which is of the order of 20 Angstrom.