Two-dimensional Laser spectroscopy to study ultrafast dynamics in materials

In both natural light harvesting systems and artificial photovoltaic cells, research on the charge and energy transfer dynamics has brought great interest. This information is critical to improve our understanding the physics and provide guidance for future development. These dynamical processes happen in the time scale of femtosecond to picosecond. Ultrafast laser spectroscopy is commonly used to detect this information. In this paper, we focus on how two-dimensional (2D) laser spectroscopy can provide an incisive tool to probe the electronic transitions, and energetic evolutions that must be understood to describe photosynthetic light-harvesting and photovoltaic charge transfer. We demonstrate its application to the study of organic dye Coumarin 102. We illustrate several capabilities of 2D spectroscopy including monitoring energy level broadening, observing energy level evolution. This information will help to determine the energy and charge transfer pathways.