Naphtho[2,3-c]thiophene-4,9-dione based polymers for efficient fullerene solar cells

New medium bandgap donor D-A1 -D-A2 type Copolymers Based on Anthra[1,2-b: 4,3-b":6,7-c"'] Trithiophene-8,12-dione Groups for High -Efficient non -fullerene Polymer Solar Cells

We synthesized a new acceptor unit anthra[1,2-b: 4,3-b': 6,7-c'']trithiophene-8,12-dione (А3Т) (A2) and then used it to design D-A₁ -D-A₂ medium bandgap donor copolymers with same thiophene (D) and A2 units but different A1 i.e., fluorinated benzothiadiazole (F-BTz) and benzothiadiazole (BTz) denoted as P130 and P131, respectively. Their detailed optical and electrochemical properties were examined. The copolymers show good solubility in common organic solvents, broad absorption in the visible spectral region from 300 nm to 700 nm, and deeper HOMO levels of -5.45 and -5.34 eV for P130 and P131, respectively. Finally, an optimized polymer solar cell based on P131 as the donor and narrow bandgap non-fullerene small molecule acceptor Y6 demonstrated a PCE of more than 11.13%. To further improve the efficiency of the non-fullerene PSC, we optimized the P130 by introducing a fluorine atom into the BTz unit, F-BTz acceptor unit, PCE PSC based on P130: Y6 active layer increased to more than 15.28 %, which is higher than that for non-fluorinated analog P131:Y6. The increase in the PCE for former PSC is attributed to the more crystalline nature and compact π-π stacking distance, leading to more balanced charge transport and reduced charge recombination. These remarkable results demonstrate that A3T-based copolymer P130 with F-BTz as the second acceptor is a promising donor material for high-performance PSCs. This article is protected by copyright. All rights reserved.