Ethynyl-linked perylene bisimide based electron acceptors for non-fullerene organic solar cells

In this work, star-shaped perylene bisimide (PBI) derivatives with spiro-aromatic cores linked with ethynyl units were developed as electron acceptors for non-fullerene organic solar cells. The ethynyl linkers were found to enhance the planarity of the conjugated backbone, resulting in high electron mobilities and near-infrared absorption. The ethynyl-linked PBI acceptors showed high power conversion efficiencies (PCEs) up to 4.27% due to the high short-circuit current density (J_sc) of 8.52 mA/cm² and fill factor (FF) of 0.59, while the PBI acceptor without ethynyl units provided a low PCE of 3.57% in non-fullerene solar cells. The results demonstrate that ethynyl units can be applied into designing new PBI electron acceptors with improved charge transport properties and photovoltaic performance.