Siloxane-decorated polymer acceptors enable humidity-tolerant air-processing and mechanical durability of all-polymer solar cells

Abstract

All-polymer solar cells (all-PSCs), leveraging conjugated polymer donors and acceptors, hold great promise for flexible electronics due to their mechanical robustness and solution processability. However, their practical application is hindered by severe efficiency losses during ambient-air processing, particularly under high humidity. Although all-polymer systems (e.g., PTB7-Th:PDI-V) exhibit inherent humidity-tolerant processing advantages over small molecule acceptor-based devices, their efficiencies remain below 8%, highlighting the unmet need for materials that simultaneously achieve high performance and humidity-tolerant air-processing. Here, we report a series of siloxane-functionalized random terpolymer acceptors, DSiX, engineered via copolymerization of Y5-I-C20-Br (PY-IT-based fused-ring monomer) and BTz-C₁-Si-Br (siloxane-decorated monomer). The hydrophobic siloxane side chains suppress moisture condensation during film formation under 90% relative humidity (RH), blocking water penetration and preserving nanoscale phase separation. Consequently, the resulting PM6:DSi10-based all-PSCs achieve a PCE of 17.37% under a N₂ atmosphere, retaining 94% efficiency (16.33%) when processed in air at 90% RH, exceeding previously reported air-processed all-PSCs. Flexible devices exhibit remarkable mechanical durability, retaining 91.3% PCE after 1000 bending cycles (radius: 5 mm). Long-term operational stability tests reveal 94% PCE retention after 550 h illumination and 83% retention under 85 °C thermal stress. This work demonstrates that siloxane functionalization is a promising strategy to decouple efficiency from high-humidity air-processing constraints, thereby advancing the practical application of all-PSCs in high-humidity air processing.