An asymmetric non-fused electron-deficient building block for low-cost polymer acceptor in all-polymer solar cells

Abstract

The development of polymerized fused-ring small molecule acceptors (FRA-PAs) has boosted the performance of all-polymer solar cells (all-PSCs). However, these FRA-PAs suffer from lengthy synthesis steps and high production costs due to the high degree of synthetic complexity for fused-ring small molecule acceptors (FRAs). Furthermore, most FRA-PAs exhibit strong batch-to-batch variation, limiting further industrial applications. Herein, we designed and synthesized asymmetric non-fused electron-deficient building block TIC-Br with a simple structure (only three synthetic steps), showing a planar configuration, excellent electron affinity, and large dipole moment. A simple polymer acceptor PTIB was further developed by polymerization of TIC-Br and sensitized fluorinated-thienyl benzodithiophene (BDT-TF-Sn). PTIB exhibits a broad absorption from 300 to 800 nm, a suitable lowest unoccupied molecular orbital (LUMO) energy level of −3.86 eV, and moderate electron mobility (1.02 × 10⁻⁴ cm² V⁻¹ s⁻¹). When matched with PM6, the device achieved the best PCE of 10.11% with a high V_OC of 0.97 V, which is one of the highest among those reported all-PSCs. More importantly, PTIB exhibits a lower synthetic complexity index (SC = 35.0%) and higher figure-of-merit values (FOM = 29.0%) than all the reported high-performance PAs. The polymer also exhibits excellent batch-to-batch reproducibility and great potential for scale-up fabrication. This study indicates that TIC-Br is a promising building block for constructing low-cost polymer acceptors for large-scale applications in all-PSCs.