A Non-Halogenated Polymer Donor Based on Imide Unit for Organic Solar Cells with Efficiency Nearly 16%

Non-halogenated polymers have great potential in the commercialization of organic solar cells (OSCs) due to their advantages in the manufacturing process. However, high-performance donor polymers are limited to a small amount of building blocks. Herein, we utilize as building block 4H-dithieno[3,2-e:2',3'-g]isoindole-4,6(5H)-dione (DTID) to design and synthesize a relevant non-halogenated polymer PBTID for active layers in OSCs. PBTID exhibits a strong absorption in the wavelength range of 400-600 nm with a distinctly wide optical bandgap of 2.06 eV, a low-lying highest occupied molecular orbital (HOMO) energy level of -5.53 eV. In addition, this polymer has a very strong aggregation effect in solution and could form nanoscale fibrils in the neat film. Consequently, when blended with the non-fullerene acceptor Y6, the devices achieve a prominent PCE of 15.8% with a high V-oc of 0.87 V. The V-oc and PCE values are one of the highest values in the non-halogenated polymer donor-based OSCs reported to date.