Synergistic construction of ternary postprocessing-free organic solar cells using a volatile solid additive containing σ-hole and Y6 isomer

Postprocessing-free organic solar cells (OSCs) with great potential for low-cost commercial production are still at a backward stage of development. Here, we designed and synthesised Iso-Y6, an isomer of the classical non-fullerene receptor Y6, by introducing F-EG with a benzothiadiazole (BTP) core and an F-substituted end group to tune the performance parameters in ternary OSCs. Its UV-vis absorption spectrum covers the visible region (400-760 nm) and extends up to the near-infrared band with a narrow optical band gap and broad absorption bands. Given the weak interactions between the S atoms of the thiophene on the backbone and the O atoms of the carbonyl group at the end-group position form a conformational lock, leading to a reduction in structural disorder, an increase in molecular planarity, and an enhancement of crystallinity. Eventual, we have constructed ternary postprocessing-free OSCs with efficiency exceeding 17.6% by combining them with the conjugated polymer donor PM6 and acceptor Y6 using the solid additive DFBB, which is capable of producing σ-hole interactions with the active layer material.