Poly(dimethylsiloxane)-block-PM6 Polymer Donors for High-Performance and Mechanically-Robust Polymer Solar Cells.

High power conversion efficiency (PCE) and stretchability are the dual requirements for the wearable application of polymer solar cells (PSCs). However, most efficient photoactive blend films are mechanically brittle. Here, we achieve highly efficient (PCE = 18%) and mechanically robust (crack-onset strain (COS) = 18%) PSCs by designing block copolymer (BCP) donors, PM6-b-PDMSx (x = 5k, 12k, and 19k). In these BCP donors, stretchable polydimethylsiloxane (PDMS) blocks are covalently linked with the PM6 blocks to effectively increase the stretchability, while preserving the electrical properties of conjugated polymer blocks. The stretchability of the BCP donors increases with a longer PDMS block, and PM6-b-PDMS 19k :L8-BO PSC exhibits a high PCE (18%) and 9-times higher COS value (18%) compared to that (COS = 2%) of the PM6:L8-BO-based PSC. Without covalent bonding of the PDMS block, PM6:L8-BO:PDMS 12k ternary blend shows inferior PCE (4%) and COS (1%) due to the phase separation between PDMS and active components. In the intrinsically-stretchable PSC, PM6-b-PDMS 19k :L8-BO blend exhibits significantly greater mechanical stability of PCE 80% (80% of the initial PCE) at 36% strain than PM6: L8-BO blend (PCE 80% at 12% strain) and PM6: L8-BO:PDMS ternary blend (PCE 80% at 4% strain). This study demonstrates an effective design strategy of BCP P D to achieve stretchable PSCs with high efficiency. This article is protected by copyright. All rights reserved.