In our laboratory, we study optoelectronic properties of polymers and their functionalities.  In other words, we study conjugated polymers as key materials based on three keywords: photons, electrons, and ions.  Using light as a tool, we aim to elucidate the properties and functions at the molecular level by directly observing ultrafast phenomena that give rise to optoelectronic properties at the molecular temporal and spatial scales.  Recently, we have been working on the development of polymer solar cells to address the global challenge of energy issues.