Iodine insertion in pentacene thin films investigated by infrared and Raman spectroscopy

Vibrational and electronic properties of iodine doped pentacene thin films were studied by Raman and infrared measurements. The observation of the polaronic transition in charged pentacene gives access to the reorganization energy of the pentacene molecules. Iodine insertion induces a modification of the CH vibrational modes located at the end and along the pentacene molecules. At low doping level, iodide ions are intercalated between the two-dimensional pentacene layers. At high doping level, iodine is inserted inside the layers of pentacene in an irreversible way, which is expected to decrease charge transport performance.