Exploring Ternary Organic Solar Cells for the Improved Efficiency of 16.5% with the Compatible Nonacyclic Carbazole-Based Nonfullerene Acceptors as the Third Component

In this study, two dithieno[3,2-b]thiophenecyclopentacarbazole (DTTC)-based nonfullerene acceptors (NFAs) named DTTC-4F-C8 and DTTC-4Cl-C9 are designed, synthesized, and incorporated as the second acceptors in PM6:Y6 binary blend to explore the performance of the ternary organic solar cells (OSCs). By incorporating a small amount of DTTC-4F-C8/DTTC-4Cl-C9 into the PM6:Y6 binary blend as the second acceptor, we achieved an elevated efficiency of 16.05%/16.55%, with simultaneously enhanced open-circuit voltage (VOC), short-circuit current-density (JSC), and fill factor (FF) values. Because of the compatibility differences between the second acceptor DTTC-4F-C8/DTTC-4Cl-C9 and the host materials PM6 and Y6, despite having comparable energy levels for the two NFAs, different photovoltaic performances are observed for the resultant ternary OSCs. The results indicate that the ternary OSCs incorporating carbazole-based NFAs DTTC-4F-C8/DTTC-4Cl-C9 as a second acceptor is a constructive method to enhance the performance of the PM6:Y6 binary host.