A polymer acceptor with double-decker configuration enhances molecular packing for high-performance all-polymer solar cells

All-polymer solar cells (all-PSCs) have seen rapid progress enabled by the development of high-performance polymer acceptors. Most polymer acceptors are based on the monomers of a classic small molecular acceptor (SMA) named Y6 by polymerizing at the position of the end groups, forming an “end-to-end” linkage. In this work, we report a completely different “core-to-core” linking mode by polymerizing the Y-series monomers at the central core position instead. This innovative strategy results in a drastically altered molecular configuration that resembles a “double decker,” with intramolecular packing between different monomer units in the same polymer. The overall molecular packing is improved, benefiting charge delocalization and charge transport. As a result, the PffBQx-T-based ternary blend achieved an outstanding efficiency of 18.7%, attributed to the enhanced absorption response, improved packing, and efficient charge dynamics. Our work demonstrates a novel polymer design rationale that serves as a promising avenue toward highly efficient and stable all-PSCs.