Metal-Complex-Functionalized Terpolymer Donors Enabling Efficient Solar Cells via Enhanced Dielectric Constant and...

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.