Ternary Organic Solar Cell with a Near-Infrared Absorbing Selenophene-Diketopyrrolopyrrole-Based Nonfullerene Acceptor and an Efficiency above 10%

A new near-IR absorbing nonfullerene acceptor (NFA), MPU4, is synthesized in three steps from an accessible selenophene-diketopyrrolopyrrole and rhodanine. The high planarity of the molecule and the extended conjugation determine that the new NFA presents a high optical absorption coefficient and a narrow bandgap. In thin films, MPU4 shows broad absorption in the visible and near-IR regions from 550 to 930 nm. When blended with a phenothiazine-based small-molecule (SM) donor, SM1, the resulting additive-free binary organic solar cell (OSC) exhibits an efficiency of 8.96% with a high open-circuit voltage (V-oc) of 0.99 V and a short-circuit current (J(sc)) of 14.91 mA cm(-2) with a remarkably low energy loss (E-loss) of 0.42 eV. This efficiency is significantly higher (24%) than that achieved with an analogous device with a thiophene-containing NFA (MPU1, 7.22%) instead of MPU4. Importantly, ternary solar cells prepared with SM1 as the donor and MPU4 and PC71BM as acceptors afford, after solvent vapor annealing, an efficiency of 10.04% with a V-oc of 0.92 V, J(sc) of 16.32 mA cm(-2), fill factor of 0.67, and E-loss of 0.49 eV. These results demonstrate the advantages of using selenophene instead of thiophene in SM OSCs.