Ultrafast infrared probes of electronic processes in materials

Ultrafast visible and near-infrared spectroscopies have been used to examine electronic processes in emerging electronic materials for many years [1-27] with particular focus on the formation and evolution of primary photoexcitations such as excitons and polarons. Many emerging materials targeting applications in flexible electronics and inexpensive photovoltaics are molecular in nature. As a consequence, the interactions of excitations and charge carriers with molecular species figure prominently in the photophysics and photochemistry of these materials [28-32]. Electronic transitions in these materials tend to be broad and inhomogeneously broadened due to conformational flexibility and thermally induced disorder. As a consequence, limited molecular structural information can be extracted from spectroscopic studies focusing solely on electronic transitions in these materials.