Conjugated Side‐Chains Optimize Giant Acceptor Compatibility with Low‐Cost Polymer Donor to Overcome the Cost‐Efficiency‐Stability Trilemma in Polymer Solar Cells

Abstract Polymer solar cells (PSCs) rely on blends of small‐molecule acceptors (SMAs) and polymer donors, but the thermodynamic relaxation of SMAs requires an oligomeric approach to enhance operational stability. However, high‐efficiency devices often depend on the expensive synthesis of oligomeric SMAs and costly polymer donors, posing a significant barrier to achieving sustainable and renewable energy. Here, the challenge is addressed through a thermodynamically derived compatibility of giant acceptors with the low‐cost polymer donor PTQ10. This is achieved by strategically employing conjugated side chains to modulate and dimerize acceptors, thereby precisely tuning their thermodynamic properties to optimize compatibility. Our synthetic route avoids toxic reagents, halogenated solvents, and harsh conditions. The dimer (DYBT) incorporating an n ‐type linker enhances crystallinity, absorption, and intramolecular superexchange coupling compared to its p ‐type counterpart, and achieves a device efficiency of 19.53%. Considering efficiency, stability, and material cost, the potential cost per kilowatt for the PTQ10:DYBT device is 0.10 $ kW −1 , while most systems exceed 10 $ kW −1 . These findings offer valuable insights for the cost‐effective oligomeric acceptors, to well pair with low‐cost donors and reduce the overall material cost of the photo‐active layer for sustainable and durable energy.