A Naphthodithiophene-Based Nonfullerene Acceptor for High-Performance Polymer Solar Cells with a Small Energy Loss
Introducing intramolecular noncovalent interactions is an effective method for enlarging the conjugated area of the donor core in nonfullerene acceptors (NFAs) to improve the photovoltaic performance. In this study, a novel NFA (NTO-4F) based on a para-substituted naphtho[1,2-b:5,6-b’]dithiophene core with alkoxy side chains was designed and synthesized, which has a featured oxygen atom at the side chains to facilitate an intramolecular noncovalent S---O interaction with thiophene at the core. NTO-4F exhibits a broad and strong absorption, suitable energy levels, and appropriate crystallinity. As a result, when NTO-4F is blended with the wide bandgap polymer, PM6, as the active layer, the optimized polymer solar cells (PSCs) achieve a power conversion efficiency (PCE) of 11.5% with a high open-circuit voltage (Voc) of 0.99 V, and a simultaneous short-circuit current density (Jsc) of 19.1 mA cm−2. The solar cells also exhibit a low energy loss of 0.56 eV. Furthermore, PM6:NTO-4F-based devices show an excellent tolerance to temperature upon thermal annealing (TA) treatment and obtain over 10% efficiency for all devices under TA treatment at 140–200 °C.