Charge transport and recombination in wide-bandgap Y6 derivatives-based organic solar cells

The power conversion efficiency of nonfullerene-based organic solar cells (OSCs) has recently exceeded 18%, thanks to the constant effort to identify the key properties governing the OSCs performance and development of better photovoltaic materials With its superior properties, low-bandgap Y6 and its derivatives have emerged as one of the most popular nonfullerene acceptors (NFAs) for OSCs. In most cases, these low bandgap NFAs were based mainly on the most widely used and successful end-group 1,1-dicyanomethylene-3-indanone (IC). On the other hand, wide-bandgap Y6 derivatives are still scarce. Attempts to increase the NFA's bandgap by incorporating electron-rich end-groups often end up with NFAs with poor performance. In this work, we compare two wide-bandgap Y6 derivatives with different end-groups, and their distinct device performance is correlated with their charge transport and recombination properties. Electronic measurements on solar cell devices and device physics results are presented to discuss charge transport and recombination within the device.