Dithienothiapyran: An Excellent Donor Block for Building High-Performance Copolymers in Nonfullerene Polymer Solar Cells

In this work, a new but excellent donor block dithienothiapyran (DTTP) was developed for constructing highly efficient wide band gap copolymer donors. Compared to dithienopyran (DTP), DTTP features weaken electron donating ability and more planar-conjugated backbones. Polymer -fluorinated benzotriazole (FBTA) based on DTTP exhibits lower highest occupied molecular orbital level (-5.30 vs -5.21 eV), higher molar extinction coefficient (1.54 X 10(5) vs 8.65 X 10(4) M-1 cm(-1)), and better crystallinity than-FBTA based on DTP, thus producing a higher device performance of 10.51% in binary blend nonfullerene polymer solar cells (NFPSCs) blended with IT-M. To improve the absorption strength of PDTTP-FBTA: devices in the shorter wavelength range and further optimize the blend morphology, a small molecule of, which has strong absorption at short wavelength (300-600 nm), was incorporated. Finally, the performance of the ternary blends was successfully enhanced to 11.57% and a very high fill factor of 76.5%. Our work provided a new but excellent donor block for building high-performance conjugated copolymers to achieve highly efficient NF-PSCs.