Side Chain Engineering of Two-Dimensional Polymeric Donors for High-Efficiency Organic Solar Cells

Two new two-dimensional (2D) conjugated polymers (Z3 and Z4) with different side chains were synthesized and applied as donor materials for organic solar cells (OSCs). The alkylthiophenyl side chains in Z4 conferred an appropriate absorption spectrum and morphology, whereas the extra thienyl incorporated in the side chains of Z3 caused stronger p-p interaction, excessive molecular aggregation, and further inferior JSC and FF. Therefore, upon blending with the acceptor Y6, Z4-based OSCs achieved a power conversion efficiency of 15.12%, which was almost 30% higher than that of Z3-based devices (10.68%). The result indicated that side-chain modification is a fine-tuning strategy for the aggregation of 2D-conjugated polymeric donors in OSCs.