Molecular Engineering of Asymmetric Narrow‐Gap Acceptors for High‐Performance Semitransparent Organic Solar Cells and Modules with Minimized Energy Losses

ABSTRACT Overcoming the inherent trade‐off between near‐infrared photon harvesting and high open‐circuit voltage losses in bulk‐heterojunction blends is critical for advancing semi‐transparent organic solar cells (ST‐OSC). Herein, we present a molecular design that combines vinylene π ‐bridge incorporation and terminal‐group halogenation to tailor energy level alignment and blend morphology with PCE10 donor. These designed materials (eC9‐V‐2Cl(‐4Cl) and eC9‐DV‐2Cl) exhibit broadened NIR absorption (up to 1020 nm) and significantly reduce non‐radiative recombination voltage loss by a maximum of ∼100 mV compared to the standard PCE10:BTP‐eC9 device. The optimized PCE10:eC9‐V‐2Cl blend, processed from a green solvent in an inverted structure, achieves a remarkable power conversion efficiency (PCE) of 14.2% for opaque devices with a minimal voltage loss of ∼250 mV. Furthermore, a simply 1D double‐layered nano‐photoinc structure (LiF/MoO 3 ) as an optical out‐coupling layer was integrated into the ST‐OSC, delivering a PCE of 9.9% with an average visible transmittance (AVT) of 42.6%, and yielding a light utilization efficiency (LUE) of 4.3%. Scaling to 5 × 5 cm 2 ST‐OSC modules, an active‐area efficiency of ≈9% was reached with a remarkably high geometric fill factor of 96.5%. These findings provide new molecular design principles for high‐performance ST‐OSCs, making these devices highly attractive for sustainable and scalable applications like energy‐saving agrivoltaic systems and aesthetically transparent solar windows.