Strengthening Near‐Infrared Photon Harvesting in Semi‐Transparent All‐Polymer Solar Cells through the Synergy of Fluorination on the Selenide Monomer Backbone

Abstract All‐polymer solar cells (all‐PSCs) offer promising potential for large‐scale manufacturing due to their remarkable mechanical and thermal stability. However, the limited capacity of polymer acceptors for near‐infrared (NIR) photon harvesting has impeded their progress in semi‐transparent (ST) all‐PSCs. Here, the study develops a pair of new NIR polymer acceptors, named PYSeF‐T and PYSe2F‐T, with mono‐/di‐fluorinated end groups capped to the selenide monomer backbone, respectively. Owing to the stronger intermolecular interaction and intramolecular charge transfer effect of the di‐fluorinated end groups with the selenide backbone, PYSe2F‐T exhibits a stronger crystallinity and a more bathochromic absorption to 1000 nm. When blended with the donor, PM6, the PY2SeF‐T‐based all‐PSC demonstrates a higher efficiency of 16.73% with a remarkable short‐circuit current ( J SC ) of 27.7 mA cm −2 , which is the highest J SC for all‐PSCs. Based on these, the ST device based on PM6:PYSe2F‐T demonstrates a superior efficiency of 12.52% with an average visible transmittance of 26.2% and a light utilization efficiency of 3.28%, outperforming the mono‐fluorinated counterpart. The work provides an in‐depth understanding of the above synergistic effects to develop NIR polymer acceptors and establishes a solid foundation for future investigations into large‐area and flexible ST all‐PSCs.