Enhancing the Electrostatic Potential To Develop High-Performance Polymer Donors via a Ternary Copolymerization Strategy.

Ternary copolymerization has been proven to be an effective method to regulate the photovoltaic properties of polymer donors. However, terpolymers synthesized using the ternary copolymerization strategy inevitably disrupt the periodic sequence distribution of the polymer backbone, resulting in increased molecular disorder and heightened main-chain entropy. Herein, we developed two terpolymer donors by introducing an electron-deficient fused-ring skeleton unit BTP with a large dipole moment into the main chain of PM6 via ternary copolymerization. We found that the presence of BTP enables terpolymers to exhibit enhanced crystallinity and increased electrostatic potential, leading to excellent miscibility and more ordered molecular packing than PM6. As a result, the maximum PCE of 19.40% was achieved for the PY5:L8-BO-based device. Overall, this work introduces a novel approach for developing high-performance terpolymer donors by combining the third component with large dipole moments to restrain main-chain disorder and enhance the intermolecular interaction force between polymer donors and acceptors.