Solar Energy Conversion in Molecular Multi-Junctions
In the TripleSolar project new functional organic molecules, polymers and hybrid materials were designed, synthesized, investigated and used in photo-electrochemical devices to convert sunlight into electrical charges and store the electrical energy created in molecules such as hydrogen. The research focused on unraveling the mechanistic details of the conversion processes and on the improving the performance of these novel devices. To convert large fractions of the solar spectrum efficiently, organic molecules tailored to absorb specific parts of the sunlight were stacked on top of each other in multi-junction cells comprising two, three, or even four different absorber layers. This strategy enables creating the chemical potential to split water into hydrogen and oxygen or to reduce carbon dioxide. By studying the mechanisms that control the three-dimensional nanoscale structure and electronic properties of the absorber layers it was possible to create efficient solar-to-electricity, solar-to-hydrogen, and solar-to-carbon monoxide devices. These artificial leafs provide a stepping stone towards a future technology in which sunlight is converted and stored directly, aiming at a main challenges of modern society to provide sustainable sources of energy to future generations. To really achieve that ambitious goal, further research and developments are required that improve on the present state of the art in terms of efficiency, stability and cost.