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

Abstract

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 (Voc) of 0.99 V and a short‐circuit current (Jsc) of 14.91 mA cm−2 with a remarkably low energy loss (Eloss) 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 Voc of 0.92 V, Jsc of 16.32 mA cm−2, fill factor of 0.67, and Eloss of 0.49 eV. These results demonstrate the advantages of using selenophene instead of thiophene in SM OSCs.