Solar energy:
A main research thrust in the XYZ lab is to establish new photophysical mechanisms that may be utilized to revolutionize solar energy conversion. One of the key questions we are focusing on is at the heart of future photovoltaic technology: How can one extract electrons and holes from photo-generated excitons in organic semiconductors or inorganic quantum dots? To answer this question, we use model material systems and state-of-the-art laser spectroscopic techniques, including femtosecond time-resolved two-photon photoemission spectroscopy (2PPE) and time-resoved second harmonic generation (SHG). As examples, recent discoveries in our lab showed how an electron and a hole is bound by the Coulomb potential across an organic semiconductor interface, how one can extract hot electrons from a photoexcited quantum dot, and how an exciton can split into two to give two electron-hole pairs from the absorption of one photon. Answers to these questions are allowing us to formulate new solar energy conversion strategies with power conversion efficiency approaching or exceeding the so-called Shockley-Queisser limit, which is the fundamental limit of conventional solar cells.

In addition to solar energy conversion, we are interested in the general challenge of understanding many-body interactions in condensed matter, such as electron-nuclear interaction leading to polaron formation in organic semiconductors and electron-electron interaction responsible for new physical properties in molecular or nanomaterials.