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

Abstract

The dielectric constant (epsilon 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 epsilon 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 epsilon 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.