Engineering ultrafast exciton dynamics to boost organic photovoltaic performance

The solar power conversion efficiencies of organic solar cells (OSC) have now increased up to 19%, closing the gap with inorganic and hybrid solar cells. The major breakthrough behind the rapid efficiency improvement is the development of non-fullerene acceptor molecules, replacing the traditional fullerene molecules as electron-accepting materials. Understanding the photophysical processes underlying these high-performance materials is crucial to OSC research. In this talk, I will present transient optical spectroscopy and structural analysis results on high-performance OSC blends based on state-of-the-art Y-type small molecule and polymeric acceptors. We find direct evidence that the interfacial D-A percolation plays a key role in suppressing interfacial charge recombination to enable efficient charge generation, and such morphology greatly improves the thermodynamic stability of the blend. Furthermore, we uncovered a new all-optical method for predicting the OSC performance of acceptor molecules, which will be a valuable tool for future material design and screening.