Non‐Halogenated Polymer Donors for High‐Performance Organic Photovoltaics

Fluorinated polymer donors such as PBDB‐TF and D18 have enabled record‐breaking organic photovoltaic (OPV) performance, but their multistep halogenation, low synthetic efficiency, and high material‐only cost (MOC) remain key barriers to large‐scale manufacturing. In this work, we evaluate a non‐halogenated analogue of PBDB‐TF in which fluorinated thiophene units are replaced by phenylthio groups (PBDB‐PS), focusing on the impact of this substitution on cost and device‐relevant properties. This modification substantially simplifies the synthetic route by eliminating halogenation steps and reduces the MOC of the polymers by approximately 29%. Despite the reduced synthetic complexity and lower cost, PBDB‐PS maintains favorable optical, electronic, and morphological properties required for efficient charge generation. When paired with state‐of‐the‐art non‐fullerene acceptors, it delivers power conversion efficiencies exceeding 20%. Overall, these results indicate that phenylthio substitution within established donor systems offers a practical route to reduce cost while preserving high photovoltaic performance.