Flexible-Linked Oligomeric Acceptors: Precise Synthesis and Enhanced Photovoltaic/Mechanical Properties for...

Intrinsically stretchable organic solar cells (IS-OSCs) are among the most promising technologies for wearable power applications. However, the development of electron acceptors that simultaneously meet the demands for high performance and mechanical stretchability remains a significant challenge. In this study, we creatively synthesized three oligomeric acceptors with flexible linkers (2YF-Br, 4YF-T, and 6YF-BT) and achieved both high efficiency and mechanical robustness in IS-OSCs. Benefiting from an improved fibrous morphology and excellent charge dynamics, rigid OSCs based on 4YF-T demonstrated a superior power conversion efficiency (PCE) of 18.76%, outperforming devices based on 2YF-Br and 6YF-BT. Additionally, the thermal stability of rigid OSCs progressively improved with increasing molecular weight, from 2YF-Br to 6YF-BT. Furthermore, the enlarged molecular weight of the acceptors significantly enhanced mechanical stretchability, with crack-onset strain (COS) values of 16.11%, 20.62%, and 25.92% for 2YF-Br, 4YF-T, and 6YF-BT, respectively. Importantly, as molecular weight increased, the mechanical robustness of IS-OSCs also improved, with 6YF-BT-based devices achieving remarkable stretchability (strain at PCE_80% = 35%). This study introduces a new class of high-molecular-weight acceptors with well-defined structures, paving the way for the advancement and practical application of IS-OSCs in wearable electronics.