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Giant molecular acceptors (GMAs) are typically designed through the conjugated linking of individual small molecule acceptors (SMAs). This design imparts an extended molecular size, elevating the glass transition temperature (Tg) relative to their SMA counterparts. Consequently, it effectively suppresses the thermodynamic relaxation of the acceptor component when blended with polymer donors to construct stable polymer solar cells (PSCs). Despite their merits, the optimization of their chemical structure for further enhancing of device performance remains challenge. Different from previous reports utilizing p‐type linkers, here, we explore an n‐type linker, specifically the benzothiadiazole unit, to dimerize the SMA units via a click‐like Knoevenagel condensation, affording BT‐DL. In comparison with B‐DL with a benzene linkage, BT‐DL exhibits significantly stronger intramolecular super‐exchange coupling, a desirable property for the acceptor component. Furthermore, BT‐DL demonstrates a higher film absorption coefficient, redshifted absorption, larger crystalline coherence, and higher electron mobility. These inherent advantages of BT‐DL translate into a higher power conversion efficiency of 18.49 % in PSCs, a substantial improvement over the 9.17 % efficiency observed in corresponding devices with B‐DL as the acceptor. Notably, the BT‐DL based device exhibits exceptional stability, retaining over 90 % of its initial efficiency even after enduring 1000 hours of thermal stress at 90 °C. This work provides a cost‐effective approach to the synthesis of n‐type linker‐dimerized GMAs, and highlight their potential advantage in enhancing intramolecular coupling for more efficient and durable photovoltaic technologies. [ABSTRACT FROM AUTHOR]

The operational stability of polymer solar cells is a critical concern with respect to the thermodynamic relaxation of acceptor‐donor‐acceptor (A‐D‐A) or A‐DA'D‐A structured small‐molecule acceptors (SMAs) within their blends with polymer donors. Giant molecule acceptors (GMAs) bearing SMAs as subunits offer a solution to this issue, while their classical synthesis via the Stille coupling suffers from low reaction efficiency and difficulty in obtaining mono‐brominated SMA, rendering the approach impractical for their large‐scale and low‐cost preparation. In this study, we present a simple and cost‐effective solution to this challenge through Lewis acid‐catalyzed Knoevenagel condensation with boron trifluoride etherate (BF3 ⋅ OEt2) as catalyst. We demonstrated that the coupling of the monoaldehyde‐terminated A‐D‐CHO unit and the methylene‐based A‐link‐A (or its silyl enol ether counterpart) substrates can be quantitatively achieved within 30 minutes in the presence of acetic anhydride, affording a variety of GMAs connected via the flexible and conjugated linkers. The photophysical properties was fully studied, yielding a high device efficiency of over 18 %. Our findings offer a promising alternative for the modular synthesis of GMAs with high yields, easier work up, and the widespread application of such methodology will undoubtedly accelerate the progress of stable polymer solar cells. [ABSTRACT FROM AUTHOR]