Metal‐Complex‐Functionalized Terpolymer Donors Enabling Efficient Solar Cells via Enhanced Dielectric Constant and Minimized Triplet Exciton Loss

The dielectric constant ( ε r ) critically influences exciton generation and subsequent dissociation into free charges, playing a pivotal role in the performance of polymer solar cells (PSCs). However, the intrinsically low ε r of conventional polymer donors leads to strong Coulombic interactions and significant energy loss ( E loss ). Herein, we address this challenge through a dielectric engineering strategy by incorporating zinc porphyrin units into the matrix polymer donor D18, resulting in a series of terpolymers D18‐Px (x = 5, 10, 15). The introduction of the zinc‐porphyrin‐based third component in the terpolymer donors significantly enhanced ε r and promoted favorable molecular aggregation. When blended with L8‐BO, the D18‐P5:L8‐BO blend film demonstrated improved miscibility, efficient charge extraction and transport, and critically minimized non‐radiative energy loss to 0.212 eV. Consequently, it achieved a record power conversion efficiency (PCE) of 20.27% for metalated complex‐based PSCs. This work showcases a facile and effective approach for designing high‐efficiency polymer donors by strategically increasing the dielectric constant and minimizing non‐radiative losses.