Challenges and Opportunities of Oligomeric Acceptors Toward Efficient and Stable Organic Photovoltaics

High power conversion efficiency (PCE) and long-term operational stability are essential prerequisites for the commercialization of organic solar cells (OSCs). Small-molecule acceptors (SMAs) have driven remarkable advances in OSC performance, enabling continuous breakthroughs in device efficiency. However, OSCs based on SMAs generally suffer from poor long-term stability, which severely limits their practical application. This instability primarily originates from the low glass transition temperatures (T_g) of SMAs, resulting in rapid molecular diffusion and aggregation, as well as morphological degradation of the active layer, leading to a subsequent decrease in device performance. Oligomeric small-molecule acceptors (OSMAs) have recently emerged as a promising molecular design strategy to overcome these challenges. OSCs incorporating OSMAs have achieved impressive PCEs approaching 20%, while simultaneously exhibiting outstanding photothermal and mechanical stability. In this perspective, we systematically review recent progress in OSMA-based OSCs and discuss the key factors governing their efficiency and stability, including molecular structure, aggregation behavior, and morphology evolution. Finally, we outline the current challenges and future opportunities for OSMA materials in advancing high-performance and durable OSC technologies.