New Anthracene-Fused Nonfullerene Acceptors for High-Efficiency Organic Solar Cells: Energy Level Modulations Enabling Match of Donor and Acceptor

Two new nonfullerene small molecule acceptors (NF-SMAs) AT-NC and AT-4Cl based on heptacyclic anthracene(cyclopentadithiophene) (AT) core and different electron-withdrawing end groups are designed and synthesized. Although the two new acceptor molecules use two different end groups, naphthyl-fused indanone (NINCN) and chlorinated INCN (INCN-2Cl) demonstrate similar light absorption. AT-4Cl with chlorinated INCN as end groups are shifted significantly due to the strong electron-withdrawing ability of chlorine atoms. Thus, desirable V-oc, and photovoltaic performance are expected to be achieved when polymer PBDB-T is used as the electron donor with AT-NC as the acceptor, and fluorinated analog PBDB-TF with down-shifted energy levels is selected to blend with AT-4Cl. Consequently, the device based on P6DB-TF:AT-4Cl yields a high power conversion efficiency of 13.27% with a slightly lower V-oc of 0.901 V, significantly enhanced J(sc) of 19.52 mA cm(-2) and fill factor of 75.5% relative to the values based on PBDB-T:AT-NC. These results demonstrate that the use of a new electron-rich AT core, together with energy levels modulations by end-group optimizations enabling the match with polymer donors, is a successful strategy to construct high-performance NF-SMAs.