Polymerized-Small-Molecule Acceptors Featuring Siloxane-Terminated Side Chains for Mechanically Robust All-Polymer Solar Cells
Jiayi He, Di Zhang, Junfeng Liu, Lvpeng Yang, Yerun Gao, Ming Shao
Abstract
Flexible and stretchable organic solar cells (OSCs) show great promise in wearable and stretchable electronic applications. However, current high-performance OSCs consisting of polymer donors (PDs) and small-molecule acceptors (SMAs) face significant challenges in achieving both high power conversion efficiency (PCE) and excellent stretch-ability. In this study, we synthesized a new polymerized-small-molecule acceptor (P-SMA) PY-SiO featuring siloxane-terminated side chains and compared its photovoltaic and mechanical performance to that of the reference PY-EH with ethylhexyl-terminated side chains. We found that the incorporation of siloxane-terminated side chains in PY-SiO enhanced the molecular aggregation and charge transport, leading to an optimized film morphology. The resultant of all-polymer solar cells (all-PSCs) based on PBDB-T/PY-SiO showed a higher PCE of 12.04% than the PY-EH-based one (10.85%). Furthermore, the siloxane-terminated side chains also increased the interchain distance and provided a larger free volume for chain rotation and reconfiguration, resulting in a higher film crack-onset strain (COS: 18.32% for PBDB-T/PY-SiO vs 11.15% for PBDB-T/PY-EH). Additionally, the PY-SiO-based stretchable all-PSCs exhibited an impressive PCE of 9.8% and retained >70% of its original PCE even under a substantial 20% strain, exceeding the performance of the PY-EH-based stretchable all-PSCs. Our result suggests the great potential of the siloxane-terminated side chain for achieving high-performance and stretchable OSCs.